History.

Historical context.

Hahnemann rejected the mainstream medicine of the late 18th century as irrational and inadvisable because it was largely ineffective and often harmful. He advocated the use

Hahnemann's concept.

The term "homeopathy" was coined by Hahnemann and first appeared in print in 1807.  Hahnemann conceived of homeopathy while translating a medical treatise by the Scottish physician and chemist William Cullen into German. Being sceptical of Cullen's theory concerning cinchona's use for curing malaria, Hahnemann ingested some bark specifically to investigate what would happen. He experienced fever, shivering and joint pain: symptoms similar to those of malaria itself. From this, Hahnemann came to believe that all effective drugs produce symptoms in healthy individuals similar to those of the diseases that they treat, in accord with the "law of similars" that had been proposed by ancient physicians. An account of the effects of eating cinchona bark noted by Oliver Wendell Holmes, and published in 1861, failed to reproduce the symptoms Hahnemann reported. Hahnemann's law of similars is an "ipse dixit" that does not derive from the scientific method. This led to the name ""homeopathy"", which comes from the "hómoios", "-like" and "páthos", "suffering".  Subsequent scientific work showed that cinchona cures malaria because it contains quinine, which kills the "Plasmodium falciparum" parasite that causes the disease; the mechanism of action is unrelated to Hahnemann's ideas.

"Provings".

Hahnemann began to test what effects substances may have produced in humans, a procedure later called "homeopathic proving". These tests required subjects to test the effects of ingesting substances by clearly recording all of their symptoms as well as the ancillary conditions under which they appeared. He published a collection of provings in 1805, and a second collection of 65 preparations appeared in his book, "Materia

Miasms and disease.

In the "Organon", Hahnemann introduced the concept of "miasms" as "infectious principles" underlying chronic disease. Hahnemann associated each miasm with specific diseases, and thought that initial exposure to miasms causes local symptoms, such as skin or venereal diseases. If, however, these symptoms were suppressed by medication, the cause went deeper and began to manifest itself as diseases of the internal organs. Homeopathy maintains that treating diseases by directly alleviating their symptoms, as is sometimes done in conventional medicine, is ineffective because all "disease can generally be traced to some latent, deep-seated, underlying chronic, or inherited tendency". The underlying imputed miasm still remains, and deep-seated ailments can be corrected only by removing the deeper disturbance of the vital force.  Hahnemann's hypotheses for the direct or remote cause of all chronic diseases (miasms) originally presented only three: psora (the itch), syphilis (venereal disease) or sycosis (fig-wart disease). Of

19th century: rise to popularity and early criticism.

Homeopathy achieved its greatest popularity in the 19th century. It was introduced to the United States in 1825 by Hans Birch Gram, a student of Hahnemann. The first homeopathic school in the US opened in 1835, and in 1844, the first US national medical association, the American Institute of Homeopathy, was established. Throughout the 19th century, dozens of homeopathic institutions appeared in Europe and the United States, and by 1900, there were 22 homeopathic colleges and 15,000 practitioners in the United States. Because medical practice of the time relied on ineffective and often dangerous treatments, patients of homeopaths often had better outcomes than those of the doctors of the time. Homeopathic preparations, even if ineffective, would almost surely cause no harm, making the users of homeopathic preparations less likely to be killed by the treatment that was supposed to be helping them. The relative success of homeopathy in the 19th century may have

Revival in the 20th century.

According to, the Nazi regime in Germany was fascinated by homeopathy, and spent large sums of money on researching its mechanisms, but without gaining a positive result. Unschuld further argues that homeopathy never subsequently took root in the United States, but remained more deeply established in European thinking. In the United States, the "Food, Drug, and Cosmetic Act" of 1938 (sponsored by Royal Copeland, a Senator from New York and homeopathic physician) recognized homeopathic preparations as drugs. In the 1950s, there were only 75 pure homeopaths practising in the U.S. However, by the mid to late 1970s, homeopathy made a significant comeback and

21st century.

Since the beginning of the 21st century, a series of meta-analyses have further shown that the therapeutic claims of homeopathy lack scientific justification. In a 2010 report, the Science and Technology Committee of the United Kingdom House of Commons recommended that homeopathy should no longer be a beneficiary of NHS funding due its lack of scientific credibility; funding ceased in 2017. In March 2015, the National Health and Medical Research Council of Australia published an information paper on homeopathy. The main findings of the report were 'there are no health conditions for which there is reliable evidence that homeopathy is effective". Reactions to the

Preparations and treatment.

Homeopathic preparations are referred to as "homeopathics" or "remedies". Practitioners rely on two types of reference when prescribing: "Materia medica" and repertories. A homeopathic "materia medica" is a collection of "drug pictures", organized alphabetically. These entries describe the symptom patterns associated with individual preparations. A homeopathic repertory is an index of disease symptoms that lists preparations associated with specific symptoms. In both cases different compilers may dispute particular inclusions. The first symptomatic homeopathic "materia medica" was arranged by Hahnemann. The first homeopathic repertory was Georg Jahr's "Symptomenkodex", published in German in 1835, and translated into English as the "Repertory to the more Characteristic Symptoms of Materia Medica" by Constantine Hering in 1838. This version was less focused on disease categories and was the forerunner to later works by James Tyler Kent. Repertories, in particular, may be very large.  Homeopathy uses animal, plant, mineral, and synthetic substances in its preparations, generally referring to them using Latin or faux-Latin names. Examples include "arsenicum album" (arsenic oxide), "natrum muriaticum" (sodium chloride or table salt), "Lachesis muta" (the venom of the bushmaster snake), "opium", and "thyroidinum" (thyroid hormone).  Some homeopaths use so-called nosodes (from the Greek "nosos", disease) made from diseased or pathological products such as fecal, urinary, and respiratory discharges, blood, and tissue. Conversely, preparations made from "healthy" specimens are called "sarcodes".  Some modern homeopaths use preparations they call "imponderables" because they do not originate from a substance but some other phenomenon presumed to have been "captured" by alcohol or lactose. Examples include X-rays and sunlight.  Other minority practices include paper preparations, where the substance and dilution are written on pieces of paper and either pinned to the patients' clothing, put in their pockets, or placed under glasses of water that are then given to the patients, and the use of radionics to manufacture preparations. Such practices have been strongly criticized by classical homeopaths as unfounded, speculative, and verging upon magic and superstition.

Preparation.

Hahnemann found that undiluted doses caused reactions, sometimes dangerous ones, so specified that preparations be given at the lowest possible dose. He found that this reduced potency as well as side-effects, but formed the view that vigorous shaking and striking on an elastic surface – a process he termed "Schütteln", translated as "succussion" – nullified this. A common explanation for his settling on this process is said to be that he found preparations subjected to agitation in transit, such as in saddle bags or in a carriage, were more "potent". Hahnemann had a saddle-maker construct a special wooden striking board covered in leather on one side and stuffed with horsehair. Insoluble solids, such as granite, diamond, and platinum,

Dilutions.

Three main logarithmic dilution scales are in regular use in homeopathy. Hahnemann created the "centesimal" or "C scale", diluting a substance by a factor of 100 at each stage. There is also a decimal dilution scale (notated as "X" or "D") in which the preparation is diluted by a factor of 10 at each stage. The centesimal scale was favoured by Hahnemann for most of his life.  A 2C dilution requires a substance to be diluted to one part in 100, and then some of that diluted solution diluted by a

Provings.

Homeopaths say that they can determine the properties of their preparations by following a method which they call "proving". As performed by Hahnemann, provings involved administering various preparations to healthy volunteers. The volunteers were then observed, often for months at a time. They were made to keep extensive journals detailing all of their symptoms at specific times throughout the day. They were forbidden from consuming coffee, tea, spices, or wine for the duration of the experiment; playing chess was also prohibited because Hahnemann considered it to be "too exciting", though they were allowed to drink beer and encouraged to exercise in moderation.  At first Hahnemann used undiluted doses for provings, but he later advocated provings with preparations at a 30C dilution (1 part in formula_1), and most modern provings are carried out using ultra-dilute preparations.

Consultation.

Homeopaths generally begin with detailed examinations of their patients' histories, including questions regarding their physical, mental and emotional states, their life circumstances and any physical or emotional illnesses..</ref> outdated source, statement can be reintroduced when a better source is found -->The homeopath then attempts to translate

Pills and active ingredients.

Homeopathic pills are made from an inert substance (often sugars, typically lactose), upon which a drop of liquid homeopathic preparation is placed and allowed to evaporate.  The process of homeopathic dilution results in no objectively detectable active ingredient in most cases, but some preparations (e.g. calendula and arnica creams) do contain pharmacologically active doses. One

Related and minority treatments and practices.

Isopathy.

Isopathy is a therapy derived from homeopathy, invented by Johann Joseph Wilhelm Lux in the 1830s. Isopathy differs from homeopathy in general in that the preparations, known as "nosodes", are made up either from things that cause the disease or from products of

Flower preparations.

Flower preparations can be produced by placing flowers in water and exposing them to sunlight. The most famous of these are the Bach flower remedies, which were developed by the physician and homeopath Edward Bach. Although the proponents of these preparations

Veterinary use.

The idea of using homeopathy as a treatment for other animals termed "veterinary homeopathy", dates back to the inception of homeopathy; Hahnemann himself wrote and spoke of the use of homeopathy in animals other than humans. The FDA has not approved homeopathic products as veterinary medicine in the U.S. In the UK, veterinary surgeons who use homeopathy may belong to the Faculty of Homeopathy and/or to the British Association of Homeopathic Veterinary Surgeons. Animals may be treated only by qualified veterinary surgeons in the UK and some other countries. Internationally, the body that supports and represents homeopathic veterinarians is the International Association for Veterinary Homeopathy.  The use of homeopathy in veterinary medicine is controversial; the

Electrohomeopathy.

Electrohomoeopathy is a derivative of homeopathy. The name refers to an electric bio-energy supposedly extracted from plants and of therapeutic value, rather than electricity in its conventional sense, combined with homeopathy.

Homeoprophylaxis.

The use of homeopathy as a preventive for serious infectious diseases is especially controversial, in the context of ill-founded public alarm over the safety of vaccines stoked by the anti-vaccination movement. Promotion of homeopathic alternatives to vaccines has been characterized as dangerous, inappropriate and irresponsible. In December 2014, the Australian homeopathy supplier Homeopathy Plus! was found to have acted deceptively in promoting homeopathic alternatives to vaccines. In 2019, an investigative journalism piece by the Telegraph revealed that homeopathy practitioners were actively discouraging patients from vaccinating their children.

Evidence and efficacy.

The "very" low concentration of homeopathic preparations, which often lack even a single molecule of the diluted substance, has been the basis of questions about the effects of the preparations since the 19th century. Modern advocates of homeopathy have proposed a concept of "water memory", according to which water "remembers" the substances mixed in it, and transmits the effect of those substances when consumed. This concept is inconsistent with the current understanding of matter, and water memory has never been demonstrated to have any detectable effect, biological or otherwise.  James Randi and the groups have highlighted the lack of active ingredients in most homeopathic products by taking large 'overdoses'. None of the hundreds of demonstrators in the UK, Australia, New Zealand, Canada and the US were injured and "no one was cured of anything, either".  Outside of the alternative medicine community, scientists have long considered homeopathy a sham or a pseudoscience, and the mainstream medical community regards it as quackery. There is an overall absence of sound statistical evidence of therapeutic efficacy, which is consistent with the lack of any biologically plausible pharmacological agent or mechanism.  Abstract concepts within theoretical physics have been invoked to suggest explanations of how or why preparations might work, including quantum entanglement, quantum nonlocality, the theory of relativity and chaos theory. Contrariwise, quantum superposition has been invoked to explain why homeopathy does "not" work in double-blind trials. However, the explanations are offered by nonspecialists within the field, and often include speculations that are incorrect in their application of the concepts and not supported by actual experiments. Several of the key concepts of homeopathy conflict with fundamental concepts of physics and chemistry. The use of quantum entanglement to explain homeopathy's purported effects is "patent nonsense", as entanglement is a delicate state that rarely lasts longer than a fraction of a second. While entanglement may result in certain aspects of individual subatomic particles acquiring linked quantum states, this does not mean the particles will mirror or duplicate each other, nor cause health-improving transformations.

Plausibility.

The proposed mechanisms for homeopathy are precluded from having any effect by the laws of physics and physical chemistry. The extreme dilutions used in homeopathic preparations usually leave not one molecule of the original substance in the final product.  A number of speculative mechanisms have been advanced to counter this, the most widely discussed being water memory, though this is now considered erroneous since short-range order in water only persists for about 1 picosecond. No evidence of stable clusters of water molecules was found when homeopathic preparations were studied using nuclear magnetic resonance, and many other

Efficacy.

No individual homeopathic preparation has been unambiguously shown by research to be different from placebo. The methodological quality of the primary research was generally low, with such problems as weaknesses in study design and reporting, small sample size, and selection bias. Since better quality trials have become available, the evidence for efficacy of homeopathy preparations has diminished; the highest-quality trials indicate that the preparations themselves exert no intrinsic effect. A review conducted in 2010 of all the pertinent studies of "best evidence" produced by the Cochrane Collaboration concluded that "the most reliable evidence – that produced by Cochrane reviews – fails to demonstrate that homeopathic medicines have effects beyond placebo."

Government level reviews.

Government-level reviews have been conducted in recent years by Switzerland (2005), the United Kingdom (2009), Australia (2015) and the European Academies' Science Advisory Council (2017).  The Swiss "programme for the evaluation of complementary medicine" (PEK) resulted in the peer-reviewed Shang publication (see "Systematic reviews and meta-analyses of efficacy") and a controversial competing analysis by homeopaths and advocates led by Gudrun Bornhöft and Peter Matthiessen, which has misleadingly been presented as a Swiss government report by homeopathy proponents, a claim that has been repudiated by the Swiss Federal Office of Public Health. The Swiss Government terminated reimbursement, though it was subsequently reinstated after a political campaign and referendum for a further six-year trial period.  The United Kingdom's House of Commons Science and Technology Committee sought written evidence and submissions from concerned parties and, following a review of all submissions, concluded that there was no compelling evidence of effect other than placebo and recommended that the Medicines and Healthcare products

Publication bias and other methodological problems.

The fact that individual randomized controlled trials have given positive results is not in contradiction with an overall lack of statistical evidence of efficacy. A small proportion of randomized controlled trials inevitably provide false-positive outcomes due to the play of chance: a statistically significant positive outcome is commonly adjudicated when the probability of it being due to chance rather than a real effect is no more than 5%―a level at which about 1 in 20 tests can be expected to show a positive result in the absence of any therapeutic effect. Furthermore, trials of low methodological quality (i.e. ones that have been inappropriately designed, conducted or reported) are prone to give misleading results. In a systematic

Systematic reviews and meta-analyses of efficacy.

Both meta-analyses, which statistically combine the results of several randomized controlled trials, and other systematic reviews of the literature are essential tools to summarize evidence of therapeutic efficacy. Early systematic reviews and meta-analyses of trials evaluating the efficacy of homeopathic preparations in comparison with placebo more often tended to generate positive results, but appeared unconvincing overall. In particular, reports of three large meta-analyses warned readers that firm conclusions could not be reached, largely due to methodological flaws in the primary studies and the difficulty in controlling for publication bias. The positive finding of one of the most prominent of the early meta-analyses, published in "The Lancet" in 1997 by Linde et al.,

Statements by major medical organizations.

Health organizations such as the UK's National Health Service, the American Medical Association, the FASEB, and the National Health and Medical Research Council of Australia, have issued statements of their conclusion that there is "no good-quality evidence that homeopathy is effective as a treatment for any health condition". In 2009, World Health Organization official Mario Raviglione criticized the use of homeopathy to treat tuberculosis; similarly, another WHO spokesperson argued there was no evidence homeopathy would be an effective treatment for diarrhoea. They warned against the use of homeopathy for serious conditions such as depression, HIV and malaria.  The American College of Medical Toxicology and the American Academy of Clinical Toxicology recommend that no one use homeopathic treatment for disease or as a preventive health measure. These organizations report that no evidence exists that homeopathic treatment is effective, but that there is evidence that using these treatments produces harm and can bring indirect health risks by delaying conventional treatment.

Explanations of perceived effects.

Science offers a variety of explanations for how homeopathy may

Purported effects in other biological systems.

While some articles have suggested that homeopathic solutions of high dilution can have statistically significant effects on organic processes including the growth of grain, histamine release by leukocytes, and enzyme reactions, such evidence is disputed since attempts to replicate them have failed. A 2007 systematic review of high-dilution experiments found that none of the experiments with positive results could be reproduced by all investigators.  In 1987, French immunologist Jacques Benveniste submitted a paper to the journal "Nature" while working at INSERM. The paper purported to have discovered that basophils, a type of white blood cell, released histamine when exposed to a homeopathic dilution of anti-immunoglobulin E antibody. The journal editors, sceptical of the results, requested that the study be replicated in

Ethics and safety.

The provision of homeopathic preparations has been described as unethical. Michael Baum, Professor Emeritus of Surgery and visiting Professor of Medical Humanities at University College London (UCL), has described homoeopathy as a "cruel deception".  Edzard Ernst, the first Professor of Complementary Medicine in the United Kingdom and a former homeopathic practitioner, has expressed his concerns about pharmacists who violate their ethical code by failing to provide customers with "necessary and relevant information" about the true nature of the homeopathic products they advertise and sell:  Patients who choose to use homeopathy rather than evidence-based medicine risk missing timely diagnosis and effective treatment of serious conditions such as cancer.  In 2013 the UK Advertising Standards Authority concluded that the Society of Homeopaths were targeting vulnerable ill people and discouraging the use of essential medical treatment while making misleading claims of efficacy for homeopathic products.  In 2015 the Federal Court of Australia imposed penalties on a homeopathic company, Homeopathy Plus! Pty Ltd and its director, for making false or misleading statements about the efficacy of the whooping cough vaccine and homeopathic remedies as an alternative to the whooping cough vaccine, in breach of the Australian Consumer Law.

Adverse effects.

Some homeopathic preparations involve poisons such as Belladonna, arsenic, and poison ivy, which are highly diluted in the homeopathic preparation. In rare cases, the original ingredients are present at detectable levels. This may be due to improper preparation or intentional low dilution. Serious adverse effects such as seizures and death have been reported or associated with some homeopathic preparations.  On September 30, 2016 the FDA issued a safety alert to consumers warning against the use of homeopathic teething gels and tablets

Lack of efficacy.

The lack of convincing scientific evidence supporting its efficacy and its use of preparations without active ingredients have led to characterizations as pseudoscience and quackery, or, in the words of a 1998 medical review, "placebo therapy at best and quackery at worst". The Russian Academy of Sciences considers homeopathy a "dangerous 'pseudoscience' that does not work", and "urges people to treat homeopathy 'on a par with magic. The Chief Medical Officer for England, Dame Sally Davies, has stated that homeopathic preparations are "rubbish" and do not serve as anything more than placebos. Jack Killen, acting deputy director of the National Center for Complementary and Alternative Medicine, says homeopathy "goes beyond current understanding

In lieu of standard medical treatment.

On clinical grounds, patients who choose to use homeopathy in preference to normal medicine risk missing timely diagnosis and effective treatment, thereby worsening the outcomes of serious conditions. Critics of homeopathy have cited individual cases of patients of homeopathy failing to receive proper treatment for diseases that could have been easily diagnosed and managed with conventional medicine and who have died as a result, and the "marketing practice" of criticizing and downplaying the effectiveness of mainstream medicine. Homeopaths claim that use of conventional medicines will "push the disease deeper" and cause more serious conditions, a process referred to as "suppression". Some homeopaths (particularly those who are non-physicians) advise their patients against immunization. Some homeopaths suggest that vaccines be replaced with homeopathic "nosodes", created from biological materials such as pus, diseased tissue, bacilli from sputum or (in the case of "bowel nosodes") faeces. While Hahnemann was opposed to such preparations, modern homeopaths often use them although there is no evidence to indicate they have any beneficial effects. Cases of homeopaths advising against the use of anti-malarial drugs have been identified. This puts visitors to the tropics who take this advice in severe danger, since homeopathic preparations are completely ineffective against the malaria parasite. Also, in one case in 2004, a homeopath instructed one of her patients to stop taking conventional medication for a heart condition, advising her on June 22, 2004 to "Stop ALL medications including homeopathic", advising her on or around August 20 that she no longer needed to take her heart medication, and adding on August 23, "She just cannot take ANY drugs – I have suggested some homeopathic remedies... I feel confident that

Regulation and prevalence.

Homeopathy is fairly common in some countries while being uncommon in others; is highly regulated in some countries and mostly unregulated in others. It is practised worldwide and professional qualifications and licences are needed in most countries. In some countries, there are no specific legal regulations concerning the use of homeopathy, while in others, licences or degrees in conventional medicine from accredited universities are required. In Germany, to become a homeopathic physician, one must attend a three-year training programme, while France, Austria and Denmark mandate licences to diagnose any illness or dispense of any product whose purpose is to treat any illness.  Some homeopathic treatment is covered by the public health service of several European countries, including France (phasing out coverage in 2021), Scotland, and Luxembourg. In England, the National Health Service recommends against prescribing homeopathic preparations, although in 2018 prescriptions worth £55,000 were written in defiance of the guidelines. However, this only represents less than 0.001% of the total NHS prescribing budget. On September 28, 2016 the UK's Committee of Advertising Practice (CAP) Compliance team wrote to homeopaths in the UK to "remind them of the rules that govern what they can and

Public opposition.

In the April 1997 edition of "FDA Consumer", William T. Jarvis, the President of the National Council Against Health Fraud, said "Homeopathy is a fraud perpetrated on the public with the government's blessing, thanks to the abuse of political power of Sen. Royal S. Copeland [chief sponsor of the 1938 Food, Drug, and Cosmetic Act]."  Mock "overdosing" on homeopathic preparations by individuals or groups in "mass suicides" have become more popular since James Randi began taking entire bottles of homeopathic sleeping pills before giving lectures. In 2010 The Merseyside Skeptics Society from the United Kingdom launched the, encouraging groups to publicly overdose as groups. In 2011 the 10:23 campaign expanded and saw sixty-nine groups participate; fifty-four submitted videos. In April 2012, at the Berkeley SkeptiCal conference, over 100 people participated in a mass overdose, taking "coffea cruda", which is supposed to treat sleeplessness.  In 2011, the non-profit educational organizations Center for Inquiry (CFI) and the associated Committee for Skeptical Inquiry (CSI) have petitioned the U.S. Food and Drug Administration (FDA) to initiate "rulemaking that would require all over-the-counter homeopathic drugs to meet the same standards of effectiveness as non-homeopathic drugs" and "to place warning labels on homeopathic drugs until such time as they are shown to be effective". In a separate petition, CFI and CSI request FDA to issue warning letters to Boiron, maker of Oscillococcinum, regarding their marketing tactic and criticize Boiron for misleading labelling and advertising of Oscillococcinum. In 2015, CFI filed comments urging the Federal Trade Commission to end the false advertising practice of homeopathy. On November 15, 2016, FTC declared that homeopathic products cannot include claims of effectiveness without "competent and reliable scientific evidence". If no such evidence exists, they must state this fact clearly on their labeling, and state that the product's claims are based only on 18th-century theories that have been discarded by modern science. Failure to do so will be considered a violation of the FTC Act. CFI in Canada is calling for persons that feel they were harmed by homeopathic products to contact them.  In July 2018 the Center for Inquiry filed a lawsuit against CVS for consumer fraud over its sale of homeopathic medicines. According to Nicholas Little, CFI's Vice President and General Counsel:  The filing in part contends that apart from being a waste of money, choosing homeopathic treatments to the exclusion of evidence-based medicines can result in worsened or prolonged symptoms, and in some cases, even death. It also claimed that CVS was selling homeopathic products on an easier-to-obtain basis than standard medication; for example on the CVS website Oscillococcinum could be purchased as a "Flu remedy", whereas the Tylenol brand could only be purchased

United States Food and Drug Administration (FDA) 2015 hearing.

On April 20–21, 2015, the FDA held a hearing on homeopathic product regulation. Invitees representing the scientific and medical community, and various pro-homeopathy stakeholders, gave testimonials on homeopathic products and the regulatory role played by the FDA. Michael de Dora, a representative from the Center for Inquiry (CFI), on behalf of the organization and dozens of doctors and scientists associated with CFI and the Committee for Skeptical Inquiry (CSI) gave a testimonial which summarized the basis of the organization's objection to homeopathic products, the harm that is done to the general public and proposed regulatory actions:  The CFI testimonial stated that the principle of homeopathy is at complete odds with the basic principles of modern biology, chemistry and physics and that decades of scientific examination of homeopathic products shows

Official conclusions and recommendations.

In March 2015, the National Health and Medical Research Council of Australia issued the following conclusions and recommendations:  In November 2016, The United States FTC issued an "Enforcement Policy Statement Regarding Marketing Claims for Over-the-Counter Homeopathic Drugs" which specified that the FTC will hold efficacy and safety claims for OTC homeopathic drugs to the same standard as other products making similar claims. A November 15, 2016, FTC press release summarized the policy as follows:  In conjunction with the 2016 FTC Enforcement Policy Statement, the FTC also released its "Homeopathic Medicine & Advertising Workshop Report", which summarizes the panel presentations and related public comments in addition to describing consumer research commissioned by the FTC. The report concluded:

Homeopathy or homoeopathy is a pseudoscientific system of alternative medicine. It was created in 1796 by Samuel Hahnemann. Its practitioners, called homeopaths, believe that a substance that causes symptoms of a disease in healthy people would cure similar symptoms in sick people; this doctrine is called "similia similibus curentur", or "like cures like". Homeopathic preparations are termed "remedies" and are made using homeopathic dilution. In this process, a chosen substance is repeatedly and thoroughly diluted. The final product is chemically indistinguishable from the diluent, which is usually either distilled water, ethanol or sugar; often, not even a single molecule of the original substance can be expected to remain in the product. Between the dilution iterations homeopaths practice hitting and/or violently shaking the product, and claim that it makes the diluent remember the original substance after its removal. Practitioners claim that such preparations, upon oral intake, can treat or cure disease.

赫尼曼相信人生病的主因是他命名的一种为“病荫”的现象,而顺势疗法为对付其而生。当时的疗剂是以反复用水或酒精稀释一特定物质制作。采用此制法是因为所使用的物质多具毒性,故以稀释以降低毒性。通常以一比十或一比一百之比例,与水、乙醇反复稀释(亦可与乳糖研磨)。赫尼曼晚年使用更高稀释倍数,认为更高的稀释度反而能增强其效力,能带出物质“隐秘、幽灵般的力量”,从而产生疗效。稀释通常持续到原物质的分子消失无踪的程度,即溶液中完全不含有原来稀释的物质。顺势疗师以参考书选取疗剂,并以病者的症状、人格物质、生理心理状况及生活史作补充考虑。


Identifying a chord's root.

Although the safest way to recognize a chord’s root is, after having reduced the chord to close spacing, to rearrange it as a stack of thirds, there are shortcuts to this: in inverted triads, the root is directly above the interval of a fourth, in inverted sevenths, it is directly above the interval of a second. With chord types, such as chords with added sixths or chords over pedal points, more than one possible chordal analysis may be possible. For example, in a tonal piece of music, the notes C, E, G, A, sounded as a chord, could be analyzed as a C major sixth chord in root position (a major triad – C, E, G – with an added sixth – A – above the root) or as a first inversion A minor seventh chord (the A minor seventh chord contains the notes A, C, E and G, but in this example, the C note, the third of the A minor chord, is in the bass). Deciding which note is the root of this chord could be determined by considering context. If the chord spelled C, E, G, A occurs immediately before a D chord (spelled D, F, A, C), most theorists and musicians would consider the first chord a minor seventh chord in first inversion, because the progression ii–V is a standard chord movement.  Various devices have been imagined to notate inverted chords and their roots:  The concept of root has been extended for the description of intervals of two notes: the interval can either be analyzed as formed from stacked thirds (with the inner notes missing): third, fifth, seventh, etc., (i.e., intervals corresponding to odd numerals), and its low note considered as the root; or as an inversion of the same: second (inversion of a seventh), fourth (inversion of a fifth), sixth (inversion of a third), etc., (intervals corresponding to even numerals) in which cases the upper note is the root. See Interval.  Some theories of common-practice tonal music admit the sixth as a possible interval above the root and consider in some cases that chords nevertheless are in root position – this is the case particularly in Riemannian theory. Chords that cannot be reduced to stacked thirds (e.g. chords of stacked fourths) may not be amenable to the concept of root, although in practice, in a lead sheet, the composer may specify that a quartal chord has a certain root (e.g., a fake book chart that indicates that a song uses an A chord, which would use the notes A, D, G. Even though this is a quartal chord, the composer has indicated that it has a root of A.)  A major scale contains seven unique pitch classes, each of which might serve as the root of a chord: Chords in atonal music are often of indeterminate root, as are equal-interval chords and mixed-interval chords; such chords are often best characterized by their interval content.

History.

The first mentions of the relation of inversion between triads appears in Otto Sigfried Harnish’s "Artis musicae" (1608), which describes "perfect" triads in which the lower note of the fifth is expressed in its own position, and "imperfect" ones, in which the "base" (i.e., "root") of the chord appears only higher. Johannes Lippius, in his "Disputatio musica tertia" (1610) and "Synopsis musicae novae" (1612), is the first to use the term "triad" ("trias harmonica"); he also uses the term "root" ("radix"), but in a slightly different meaning. Thomas Campion, "A New Way of Making Fowre Parts in Conterpoint", London, ca. 1618, notes that when chords are in first inversions (sixths), the bass is not "a true base", which is implicitly a third lower. Campion's "true base" is the root of the chord.  Full recognition of the relationship between the triad and its inversions is generally credited to Jean-Philippe Rameau and his "Traité d’harmonie" (1722). Rameau was not the first to discover triadic inversion, but his main achievement is to have recognized the importance of the succession of roots (or of chords identified by their roots) for the construction of tonality (see below, Root progressions).

Possible mathematical and scientific basis.

The concept of root has some basis in the physical properties of harmonic sounds. When two notes or more notes from the harmonic series are played at the same time, people sometimes perceive the fundamental note of the series, even if that note is not present (see Missing fundamental). This property has been used in organ building for the production of low notes by resultant tones. Andreas Werckmeister’s "Harmonologia" (1702) describes the major triad in root position and in first inversion in terms of the harmonic series, but this description cannot be extended to the minor triad.  Hindemith, who described the chromatic scale as resulting from "the juxtaposition of vibrating units in the proportions of the simple numbers from 1 to 6", i.e. from the intervals corresponding to harmonic partials 1 to 6, called the fundamental of this harmonic series the "root" of the scale. From this root, he then derived a series of notes in diminishing degree of relationship, which he called "Series 1" and on which he built a system of composition. This system however has been criticized for being based generically in theory derived rules and not on perception of specific instances.

Assumed root.

An assumed root (also absent, or omitted root) is "when a chord does not contain a root ([which is] not unusual)". In any context, it is the unperformed root of a performed chord. This 'assumption' may be established by the interaction of physics and perception, or by pure convention. "We only interpret a chord as having its root omitted when the habits of the ear make it absolutely necessary for us to think of the absent root in such a place."[emphasis original]. "We do not acknowledge omitted Roots except in cases where the mind is "necessarily" conscious of them... There are also cases in instrumental accompaniment in which the root having been struck at the commencement of a measure, the ear "feels" it through the rest of the measure" (emphasis in original).  In guitar tablature, this may be indicated, "to show you where the root would be", and to assist one with, "align[ing] the chord shape at the appropriate fret", with an assumed root in grey, other notes in white, and a sounded root in black.  An example of an assumed root is the diminished seventh chord, of which a note a major third below the chord is often assumed to be the absent root, making it a ninth chord. The diminished seventh chord affords, "singular facilities for modulation", as it may be notated four ways, to represent four different assumed roots.

In jazz.

In jazz and jazz fusion, roots are often omitted from chords when chord-playing musicians (e.g., electric guitar, piano, Hammond organ) are improvising chords in an ensemble that includes a bass player (either double bass, electric bass, or other bass instruments), because the bass player plays the root. For example, if a band is playing a tune in the key of C major, if there is a dominant seventh chord played on the dominant chord (i.e., G), the chord-playing musicians typically do not play the "G" note in their voicing of the chord, as they expect the bass player to play the root. The chord playing musicians usually play a voicing that includes the third, seventh, and additional extensions (often the ninth and thirteenth, even if they are not specified in the chord chart). Thus a typical voicing by a chord-playing musician for a G chord would be the notes B and F (the third and flat seventh of the chord), along with the notes A and E (the ninth and thirteenth of the G chord). One possible voicing for this G chord would be the notes B, E, F, A (the third, thirteenth, seventh and ninth of the G chord). (Note: the thirteenth interval is the same "pitch class" as the sixth, except that it is one octave higher; the ninth is the same "pitch class" as the second interval, except that it is one octave higher.)

Root progressions in music.

The fundamental bass ("basse fondamentale") is a concept proposed by Jean-Philippe Rameau, derived from the thoroughbass, to notate what would today be called the progression of chord roots rather than the actual lowest note found in the music, the bassline. From this Rameau formed rules for the progression of chords based on the intervals between their roots. Subsequently, music theory has typically treated chordal roots as the defining feature of harmony.  Roman numeral analysis may be said to derive from the theory of the fundamental bass, although it does not particularly theorize the succession of roots. The theory of the fundamental bass properly speaking has been revived in the 20th century by Arnold Schoenberg, Yizhak Sadaï and Nicolas Meeùs.

In music theory, the concept of root is the idea that a chord can be represented and named by one of its notes. It is linked to harmonic thinking— the idea that vertical aggregates of notes can form a single unit, a chord. It is in this sense that one speaks of a "C chord" or a "chord on C"—a chord built from C and of which the note (or pitch) C is the root. When a chord is referred to in Classical music or popular music without a reference to what type of chord it is (either major or minor, in most cases), it is assumed a major triad, which for C contains the notes C, E and G. The root need not be the bass note, the lowest note of the chord: the concept of root is linked to that of the inversion of chords, which is derived from the notion of invertible counterpoint. In this concept, chords can be inverted while still retaining their root.

在音乐理论中,我们称一个和弦的根音,是作为该和弦建立在其之上的那个音符。举例来说,拿C当根音的三和弦用的三个音会是C-E-G。基本上,和弦的名称便是以根音来命名的。因此,以C为根音的三和弦称作C和弦。根音时常跟音阶的主音混淆,后者是用来代表音阶的音符,而不是和弦的音符。


History.

In the early 1980s, there was no standardized means of synchronizing electronic musical instruments manufactured by different companies. Manufacturers had their own proprietary standards to synchronize instruments, such as CV/gate and Digital Control Bus (DCB). Roland founder Ikutaro Kakehashi felt the lack of standardization was limiting the growth of the electronic music industry. In June 1981, he proposed developing a standard to Oberheim Electronics founder Tom Oberheim, who had developed his own proprietary interface, the Oberheim System.  Kakehashi felt the Oberheim System was too cumbersome, and spoke to Sequential Circuits president Dave Smith about creating a simpler, cheaper alternative. While Smith discussed the concept with American companies, Kakehashi discussed it with Japanese companies Yamaha, Korg and Kawai. Representatives from all companies met to discuss the idea in October. Initially, only Sequential Circuits and the Japanese companies were interested.Using Roland's DCB as a basis, Smith and Sequential Circuits engineer Chet Wood devised a universal synthesizer interface to allow communication between equipment from different manufacturers. Smith and Wood proposed this standard in a paper, "Universal Synthesizer Interface," at the Audio Engineering

Impact.

MIDI's appeal was originally limited to professional musicians and record producers who wanted to use electronic instruments in the production of popular music. The standard allowed different instruments to communicate with each other and with computers, and this spurred a rapid expansion of the sales and production of electronic instruments and music software. This interoperability allowed one device to be controlled from another, which reduced the amount of hardware musicians needed. MIDI's introduction coincided with the dawn of the personal computer era and the introduction of samplers and digital synthesizers. The creative

Applications.

Instrument control.

MIDI was invented so that electronic or digital musical instruments could communicate with each other and so that one instrument can control another. For example, a MIDI-compatible sequencer can trigger beats produced by a drum sound module. Analog synthesizers that have no digital component and were built prior to MIDI's development can be retrofit with kits that convert MIDI messages into analog control voltages. When a note is played on a MIDI instrument, it generates a digital MIDI message that can be used to trigger a note on another instrument. The capability for remote control allows full-sized instruments to be replaced with smaller sound modules, and allows musicians to combine instruments to achieve a fuller sound,

Composition.

MIDI events can be sequenced with computer software, or in specialized hardware music workstations. Many digital audio workstations (DAWs) are specifically designed to work with MIDI as an integral component. MIDI piano rolls have been developed in many DAWs so that the recorded MIDI messages can be easily modified. These tools allow composers to audition and edit their work much more quickly and efficiently than did older solutions, such as multitrack recording.  Because MIDI is a set of commands that create sound, MIDI sequences can be manipulated in

Use with computers.

The personal computer market stabilized at the same time that MIDI appeared, and computers became a viable option for music production. In 1983 computers started to play a role in mainstream music production. In the years immediately after the 1983 ratification of the MIDI specification, MIDI features were adapted to several early computer platforms. NEC's PC-88 and PC-98 began supporting MIDI as early as 1982. The Yamaha CX5M introduced MIDI support and sequencing in an MSX system in 1984.  The spread of MIDI on personal computers was largely facilitated by Roland Corporation's MPU-401, released in 1984, as the first MIDI-equipped PC sound card, capable of MIDI sound processing and sequencing.

Standard files.

The Standard MIDI File (SMF) is a file format that provides a standardized way for music sequences to be saved, transported, and opened in other systems. The standard was developed and is maintained by the MMA, and usually uses a codice_1 extension.The compact size of these files led to their widespread use in computers, mobile phone ringtones, webpage authoring and musical greeting cards. These files are intended for universal use and include such information as note values, timing and track names. Lyrics may be included as metadata, and can be displayed by karaoke machines.  SMFs are created as an export format of software sequencers or hardware workstations. They organize MIDI messages into one or more parallel tracks, and timestamp the events so that they can be played back in sequence. A header contains the arrangement's track count, tempo and which of three SMF formats the file is in. A type 0 file contains the entire performance, merged onto a single track, while type 1 files may contain any number of tracks that are performed in synchrony. Type 2 files are rarely used and store multiple arrangements, with each arrangement having its

Other applications.

MIDI has been adopted as a control protocol in a number of non-musical applications. MIDI Show Control uses MIDI commands to direct stage lighting systems and to trigger cued events in theatrical productions. VJs and turntablists use it to cue clips, and to synchronize equipment, and recording systems use it for synchronization and automation. Apple Motion allows control of animation parameters through MIDI. The 1987 first-person shooter game "MIDI Maze"

Devices.

Connectors.

The cables terminate in a 180° five-pin DIN connector. Standard applications use only three of the five conductors: a ground wire, and a balanced pair of conductors that carry a +5 volt signal. This connector configuration can only carry messages in one direction, so a second cable is necessary for two-way communication. Some proprietary applications, such as phantom-powered footswitch controllers, use the spare pins for direct current (DC) power transmission.  Opto-isolators keep MIDI devices electrically separated from their connectors, which prevents the occurrence of ground loops and protects equipment from voltage spikes. There is no error detection capability in MIDI, so the maximum cable length is set at 15 meters (50 feet) to limit interference.  Most devices do not copy messages from their input to their output port. A third type of port, the "thru" port, emits a copy of everything received at the input port, allowing data to be forwarded to another instrument in a "daisy chain" arrangement. Not all devices contain thru ports, and devices that lack the ability to generate MIDI data, such as effects units and sound modules, may not include out ports.

Management devices.

Each device in a daisy chain adds delay to the system. This is avoided with a MIDI thru box, which contains several outputs that provide an exact copy of the box's input signal. A MIDI merger is able to combine the input from multiple devices into a single stream, and allows multiple controllers to be connected to a single device. A MIDI switcher allows switching between multiple devices, and eliminates the need to physically repatch cables. MIDI patch bays combine

Interfaces.

A computer MIDI interface's main function is to match clock speeds between the MIDI device and the computer. Some computer sound cards include a standard MIDI connector, whereas others connect by any of various means that include the D-subminiature DA-15 game port, USB, FireWire, Ethernet or a proprietary connection. The increasing use of USB connectors in the 2000s has led to the availability of MIDI-to-USB data interfaces that can transfer MIDI channels to USB-equipped computers. Some MIDI keyboard controllers are equipped with USB jacks, and can be plugged into computers that

Controllers.

There are two types of MIDI controllers: performance controllers that generate notes and are used to perform music, and controllers that may not send notes, but transmit other types of real-time events. Many devices are some combination of the two types.  Keyboards are by far the most common type of MIDI controller. MIDI was designed with keyboards in mind, and any controller that is not a keyboard is considered an "alternative" controller. This was seen as a limitation by composers who were not interested in keyboard-based music, but the standard proved flexible, and MIDI compatibility was introduced to other types of controllers, including guitars, stringed and wind instruments, drums and specialized and experimental controllers. Other controllers include drum controllers and wind controllers, which can emulate the playing of drum kit and wind instruments, respectively. Nevertheless,

Instruments.

A MIDI instrument contains ports to send and receive MIDI signals, a CPU to process those signals, an interface that allows user programming, audio circuitry to generate sound, and controllers. The operating system and factory sounds are often stored in a Read-only memory (ROM) unit.  A MIDI instrument can also be a stand-alone module (without a piano style keyboard) consisting of a General MIDI soundboard (GM, GS and XG), onboard editing, including transposing/pitch changes, MIDI instrument changes and adjusting volume, pan, reverb levels and other MIDI controllers. Typically, the MIDI Module includes a large screen, so the user can view information for the currently selected function. Features can include scrolling lyrics, usually embedded in a MIDI file or karaoke MIDI, playlists, song library and editing screens. Some MIDI Modules include a Harmonizer and the ability to playback and transpose MP3 audio files.

Synthesizers.

Synthesizers may employ any of a variety of sound generation techniques. They may include an integrated keyboard, or may exist as "sound modules" or "expanders" that generate sounds when

Samplers.

A sampler can record and digitize audio, store it in random-access memory (RAM), and play it back. Samplers typically allow a user to edit a sample and save it to a hard disk, apply effects to it, and shape it with the same tools that synthesizers use. They also may be available in either keyboard or

Drum machines.

Drum machines typically are sample playback devices that specialize in drum and percussion sounds. They commonly contain a sequencer that allows the creation of drum patterns, and allows

Workstations and hardware sequencers.

Sequencer technology predates MIDI. Analog sequencers use CV/Gate signals to control pre-MIDI analog synthesizers. MIDI sequencers typically are operated by transport features modeled after those of tape decks. They are capable of recording MIDI performances, and arranging them into individual tracks along a multitrack recording concept. Music workstations combine controller keyboards with an internal sound generator and a sequencer. These can be used to build complete arrangements and play them back using their own internal sounds, and function as self-contained music production studios. They commonly include file storage and transfer capabilities.

Effects devices.

Some effects units can be remotely controlled via MIDI. For example,

Technical specifications.

MIDI messages are made up of 8-bit "words" (commonly called "bytes") that are transmitted serially at a rate of 31.25 kbit/s. This rate was chosen because it is an exact division of 1 MHz, the operational speed of many early microprocessors. The first bit of each word identifies whether the word is a status byte or a data byte, and is followed by seven bits of information. A start bit and a stop bit are added to each byte for framing purposes, so a MIDI byte requires ten bits for transmission.  A MIDI link can carry sixteen independent channels of information. The channels are numbered 1–16, but their actual corresponding binary encoding is 0–15. A device can be configured to only listen to specific channels and to ignore the messages sent on other channels ("Omni Off" mode), or it can listen to all channels, effectively ignoring the channel address ("Omni On"). An individual device may be monophonic (the start of a new "note-on" MIDI command implies the termination of the previous note), or polyphonic (multiple notes may be sounding at once, until the polyphony limit of the instrument is reached, or the notes reach the end of their decay envelope, or explicit "note-off" MIDI commands are received). Receiving devices can typically be set to all four combinations of "omni off/on" versus "mono/poly" modes.

Messages.

A MIDI message is an instruction that controls some aspect of the receiving device. A MIDI message consists of a status byte, which indicates the type of the message, followed by up to two data bytes that contain the parameters. MIDI messages can be "channel messages" sent on only one of the 16 channels and monitored only by devices on that channel, or "system messages" that all devices receive. Each receiving device ignores data not relevant to its function. There are

System Exclusive messages.

System Exclusive (SysEx) messages are a major reason for the flexibility and longevity of the MIDI standard. Manufacturers use them to create proprietary messages that control their equipment more thoroughly than standard MIDI messages could. SysEx messages are addressed to a specific device in a system. Each manufacturer has

Implementation chart.

Devices typically do not respond to every type of message defined by the MIDI specification. The MIDI implementation chart was standardized by the MMA as a way for users to see what specific capabilities an instrument has, and how it responds to messages. A specific MIDI Implementation Chart is usually published for each MIDI device within the device documentation.

Electrical specifications.

The MIDI 1.0 specification for the electrical interface is based on a fully isolated current loop. The MIDI out port nominally sources a +5 volt source through a 220 ohm resistor out through pin 4 on the MIDI out DIN connector, in on pin 4 of the receiving device's MIDI in DIN connector, through a 220 ohm protection resistor and the LED of an opto-isolator. The current then returns via pin 5 on the MIDI in port to the originating device's MIDI out port pin 5, again with a 220 ohm resistor in the path, giving a nominal current of about 5

Extensions.

MIDI's flexibility and widespread adoption have led to many refinements of the standard, and have enabled its application to purposes beyond those for which it was originally intended.

General MIDI.

MIDI allows selection of an instrument's sounds through program change messages, but there is no guarantee that any two instruments have the same sound at a given program location. Program #0 may be a piano on one instrument, or a flute on another. The General MIDI (GM) standard was established in 1991, and provides a standardized sound bank that allows a Standard MIDI File created on one device to sound similar when played back on another. GM specifies a bank of 128 sounds arranged into 16 families of eight related instruments, and assigns a specific program number to each instrument. Percussion instruments are placed on channel 10, and a specific MIDI note value is mapped to each percussion sound. GM-compliant

GS, XG, and GM2.

A general opinion quickly formed that the GM's 128-instrument sound set was not large enough. Roland's General Standard, or GS, system included additional sounds, drumkits and effects, provided a "bank select" command that could be used to access them, and used MIDI Non-Registered Parameter Numbers (NRPNs) to access its new features. Yamaha's Extended General MIDI, or XG, followed in 1994. XG similarly offered extra sounds, drumkits and effects, but used standard controllers instead of NRPNs for editing, and increased polyphony

Tuning standard.

Most MIDI synthesizers use equal temperament tuning. The MIDI tuning standard (MTS), ratified in 1992, allows alternate tunings. MTS allows microtunings that can be

Time code.

A sequencer can drive a MIDI system with its internal clock, but when a system contains multiple sequencers, they must synchronize to a common clock. MIDI Time Code (MTC), developed by Digidesign, implements SysEx messages that have been developed specifically for timing purposes, and

Machine control.

MIDI Machine Control (MMC) consists of a set of SysEx commands that operate the transport controls of hardware recording devices. MMC lets a sequencer send "Start", "Stop", and

Show control.

MIDI Show Control (MSC) is a set of SysEx commands for sequencing and remotely cueing show control

Timestamping.

One solution to MIDI timing problems is to mark MIDI events with the times they are to be played, and store them in a buffer in the MIDI interface ahead of time. Sending data beforehand reduces the likelihood that a busy passage can send a large amount of information that overwhelms the transmission link. Once stored in the

Sample dump standard.

An unforeseen capability of SysEx messages was their use for transporting audio samples between instruments. This led to the development of the sample dump standard

Downloadable sounds.

The Downloadable Sounds (DLS) specification, ratified in 1997, allows mobile devices and computer sound cards to expand their wave tables with downloadable

MIDI Polyphonic Expression.

MIDI Polyphonic Expression (MPE) is a method of using MIDI that enables pitch bend, and other dimensions of expressive control, to be adjusted continuously for individual notes. MPE works by assigning each note to its own MIDI channel so that particular messages can be applied to each note individually. The specifications

Alternative hardware transports.

In addition to the original 31.25 kbit/s current-loop transported on 5-pin DIN, other connectors have been used for the same electrical data, and transmission of MIDI streams in different forms over USB, IEEE 1394 a.k.a. FireWire, and Ethernet is now common. Some samplers and hard drive recorders can also pass MIDI data between each other over SCSI.

USB and FireWire.

Members of the USB-IF in 1999 developed a standard for MIDI over USB, the "Universal Serial Bus Device Class Definition for MIDI Devices" MIDI over USB has become increasingly common as other interfaces that had been used for MIDI connections (serial, joystick, etc.) disappeared from personal computers. Linux, Microsoft Windows, Macintosh OS X, and Apple iOS operating systems include standard class drivers to support devices that use the "Universal

XLR connectors.

The Octave-Plateau Voyetra-8 synthesizer was an early MIDI implementation using XLR3 connectors in place of the 5-pin DIN. It was released in the pre-MIDI years and later retrofitted with a MIDI interface but keeping its XLR connector.

Serial parallel, and joystick port.

As computer-based studio setups became common, MIDI devices that could connect directly to a computer became available. These typically used the 8-pin mini-DIN connector that was used by Apple for serial and printer ports prior to the introduction of the Blue & White G3 models. MIDI interfaces intended for use as the

mLAN.

Yamaha introduced the mLAN protocol in 1999. It was conceived as a Local Area Network for musical instruments using FireWire as the transport, and was designed to carry multiple MIDI channels together with multichannel digital audio, data file transfers, and time code. mLan was used in a number of Yamaha products, notably digital mixing consoles and the Motif synthesizer, and in third-party products such as the PreSonus FIREstation and the Korg Triton Studio. No new mLan products have been released since 2007.

Ethernet and Internet.

Computer network implementations of MIDI provide network routing capabilities, and the high-bandwidth channel that earlier alternatives to MIDI, such as ZIPI, were intended to bring. Proprietary implementations have existed since the 1980s,

Wireless.

Systems for wireless MIDI transmission have been available since the 1980s. Several commercially available transmitters allow wireless transmission of MIDI and OSC signals over Wi-Fi and Bluetooth. iOS devices are

TRS minijack.

Some devices use standard 3.5 mm TRS audio minijack connectors for MIDI data, including the Korg Electribe 2 and the Arturia Beatstep Pro. Both come with adaptors that

MIDI 2.0.

The MIDI 2.0 standard was presented on 17 January 2020 at the Winter NAMM Show in Anaheim, California at a session titled "Strategic Overview and Introduction to MIDI 2.0" by representatives Yamaha, Roli, Microsoft, Google, and the MIDI Association. This significant update adds bidirectional communication while maintaining backwards compatibility.  The new protocol has been researched since 2005. Prototype devices have been shown privately at NAMM using wired and wireless connections and licensing and product certification policies have been developed, however no projected release date was announced. Proposed physical layer and transport layer included Ethernet-based protocols such as RTP MIDI and Audio Video Bridging/Time-Sensitive Networking, as well as User Datagram Protocol (UDP)-based transport.  AMEI and MMA announced that complete specifications will be published following interoperability testing of prototype implementations from major manufacturers such as Google, Yamaha, Steinberg, Roland, Ableton, Native Instruments, and ROLI, among others. In January 2020, Roland announced the A-88mkII controller keyboard that supports MIDI 2.0.  MIDI 2.0 includes MIDI Capability Inquiry specification for property exchange and profiles, and the new Universal MIDI Packet format for high-speed transports which supports both MIDI 1.0 and MIDI 2.0 voice messages.

MIDI Capability Inquiry.

MIDI Capability Inquiry (MIDI-CI) specifies Universal SysEx messages to implement device profiles, parameter exchange, and MIDI protocol negotiation. The specifications were released in November 2017 by AMEI and in January 2018 by the MMA.  Parameter exchange defines methods to inquiry device capabilities, such as supported controllers,

Universal MIDI Packet.

MIDI 2.0 defines a new Universal MIDI Packet format, which contains messages of varying length (32, 64, 96 or 128 bits) depending on the payload type. This new packet format supports a total of 256 MIDI channels, organized in 16 groups of 16 channels; each group can carry either a MIDI 1.0

New protocol.

As of January 2019, the draft specification of the new protocol supports all core messages that also exist in MIDI 1.0, but extends their precision and resolution; it also

Data transfer formats.

System Exclusive 8 messages use a new 8-bit data format, based on Universal System Exclusive

MIDI (; an acronym for Musical Instrument Digital Interface) is a technical standard that describes a communications protocol, digital interface, and electrical connectors that connect a wide variety of electronic musical instruments, computers, and related audio devices for playing, editing and recording music. The specification originates in a paper published by Dave Smith and Chet Wood then of Sequential Circuits at the October 1981 Audio Engineering Society conference in New York City then titled "Universal Synthesizer Interface." A single MIDI link through a MIDI cable can carry up to sixteen channels of information, each of which can be routed to a separate device or instrument. This could be sixteen different digital instruments, for example. MIDI carries event messages, data that specify the instructions for music, including a note's notation, pitch, velocity (which is heard typically as loudness or softness of volume), vibrato, panning to the right or left of stereo, and clock signals (which set tempo). When a musician plays a MIDI instrument, all of the key presses, button presses, knob turns and slider changes are converted into MIDI data. One common MIDI application is to play a MIDI keyboard or other controller and use it to trigger a digital sound module (which contains synthesized musical sounds) to generate sounds, which the audience hears produced by a keyboard amplifier. MIDI data can be transferred via MIDI or USB cable, or recorded to a sequencer or digital audio workstation to be edited or played back.

音乐数码接口(Musical Instrument Digital Interface,简称MIDI)是一个工业标准的电子通讯协定,为电子乐器等演奏装置(如合成器)定义各种音符或弹奏码,容许电子乐器、电脑、手机或其它的舞台演出配备彼此连接,调整和同步,得以即时交换演奏资料。


History.

Background.

The MP3 lossy audio data compression algorithm takes advantage of a perceptual limitation of human hearing called auditory masking. In 1894, the American physicist Alfred M. Mayer reported that a tone could be rendered inaudible by another tone of lower frequency. In 1959, Richard Ehmer described a complete set of auditory curves regarding this phenomenon. Between 1967 and 1974, Eberhard F. Zwicker did work in the areas of tuning and masking of critical frequency bands, which in turn built on the fundamental research in the area from Harvey Fletcher and his collaborators at Bell Labs.  Perceptual coding was first used for speech coding compression with linear predictive coding (LPC), which has origins in the work of Fumitada Itakura (Nagoya University) and Shuzo Saito (Nippon Telegraph and Telephone) in 1966. In 1978, Bishnu S. Atal and Manfred R. Schroeder at Bell Labs proposed an LPC speech codec, called adaptive predictive coding, that used a psychoacoustic coding algorithm exploiting the masking properties of the human ear. Further optimisation by Schroeder and Atal with J.L. Hall was later reported in a 1979

Development.

The genesis of the MP3 technology is fully described in a paper from Professor Hans Musmann, who chaired the ISO MPEG Audio group for several years. In December 1988, MPEG called for an audio coding standard. In June 1989, 14 audio coding algorithms were submitted. Because of certain similarities between these coding proposals, they were clustered into four development groups. The first group was MUSICAM, by Matsushita, CCETT, ITT and Philips. The second group was ASPEC, by AT&T, France Telecom, Fraunhofer Gesellschaft, Deutsche and Thomson-Brandt. The third group was ATAC, by Fujitsu, JVC, NEC and Sony. And the fourth group was SB-ADPCM, by NTT and BTRL.  The immediate predecessors of MP3 were "Optimum Coding in the

Standardization.

In 1991, there were two available proposals that were assessed for an MPEG audio standard: MUSICAM (Masking pattern adapted Universal Subband Integrated Coding And Multiplexing) and ASPEC (Adaptive Spectral Perceptual Entropy Coding). The MUSICAM technique, proposed by Philips (Netherlands), CCETT (France), the Institute for Broadcast Technology (Germany), and Matsushita (Japan), was chosen due to its simplicity and error robustness, as well as for its high level of computational efficiency. The MUSICAM format, based on sub-band coding, became the basis for the MPEG Audio compression format, incorporating, for example, its frame structure, header format, sample rates, etc.  While much of MUSICAM technology and ideas were incorporated into the definition of MPEG Audio Layer I and Layer II, the filter bank alone and the data structure based on 1152 samples framing (file format and byte oriented stream) of MUSICAM remained in the Layer III (MP3) format, as part of the computationally inefficient hybrid filter bank. Under the chairmanship of Professor Musmann of the Leibniz University Hannover, the editing of the standard was delegated to Leon van de Kerkhof (Netherlands), Gerhard

Going public.

A reference simulation software implementation, written in the C language and later known as "ISO 11172-5", was developed (in 1991–1996) by the members of the ISO MPEG Audio committee in order to produce bit compliant MPEG Audio files (Layer 1, Layer 2, Layer 3). It was approved as a committee draft of ISO/IEC technical report in March 1994 and printed as document CD 11172-5 in April 1994. It was approved as a draft technical report (DTR/DIS) in November 1994, finalized in 1996 and published as international standard ISO/IEC TR 11172-5:1998 in 1998. The reference software in C language was later published as a freely available ISO standard. Working in non-real time on a number of operating systems, it was able to demonstrate the first real

Fraunhofer example implementation.

A hacker named SoloH discovered the source code of the "dist10" MPEG reference implementation shortly after the release on the servers of the University of Erlangen. He developed a higher-quality version and spread it on the internet. This code started the widespread CD ripping and digital music distribution as MP3 over the internet.

Internet distribution.

In the second half of the 1990s, MP3 files began to spread on the Internet, often via underground pirated song networks. The first known experiment in Internet distribution was organized in the early 1990s by the Internet Underground Music Archive, better known by the acronym IUMA. After some experiments using uncompressed audio files, this archive started to deliver on the native worldwide low speed Internet some compressed MPEG Audio files using the MP2 (Layer II) format and later on used MP3 files when the standard was fully completed. The popularity of MP3s began to rise rapidly with the advent of Nullsoft's audio player Winamp, released in 1997. In 1998, the first portable solid state digital audio player

Design.

File structure.

An MP3 file is made up of MP3 frames, which consist of a header and a data block. This sequence of frames is called an elementary stream. Due to the "bit reservoir", frames are not independent items and cannot usually be extracted on arbitrary frame boundaries. The MP3 Data blocks contain the (compressed) audio information in terms of frequencies and amplitudes. The diagram shows that the MP3 Header consists of a sync word,

Encoding and decoding.

The MP3 encoding algorithm is generally split into four parts. Part 1 divides the audio signal into smaller pieces, called frames, and a modified discrete cosine transform (MDCT) filter is then performed on the output. Part 2 passes the sample into a 1024-point fast Fourier transform (FFT), then the psychoacoustic model is applied and another MDCT filter is performed on the output. Part 3 quantifies and encodes each sample, known as noise allocation, which adjusts itself in order to meet the bit rate and sound masking requirements. Part 4 formats the bitstream, called an audio

Quality.

When performing lossy audio encoding, such as creating an MP3 data stream, there is a trade-off between the amount of data generated and the sound quality of the results. The person generating an MP3 selects a bit rate, which specifies how many kilobits per second of audio is desired. The higher the bit rate, the larger the MP3 data stream will be, and, generally, the closer it will sound to the original recording. With too low a bit rate, compression artifacts (i.e., sounds that were not present in the original recording) may be audible in the reproduction. Some audio is hard to compress because of its randomness and sharp attacks. When this type of

Bit rate.

Bitrate is the product of the sample rate and number of bits per sample used to encode the music. CD audio is 44100 samples per second. The number of bits per sample also depends on the number of audio channels. CD is stereo and 16 bits per channel. So, multiplying 44100 by 32 gives 1411200—the bitrate of uncompressed CD digital audio. MP3 was designed to encode this 1411 kbit/s data at 320 kbit/s or less. As less complex passages are detected by MP3 algorithms then lower bitrates may be employed. When using MPEG-2 instead of MPEG-1, MP3 supports only lower sampling rates (16000, 22050 or 24000 samples per second) and offers choices of bitrate as low as 8 kbit/s but no higher than 160 kbit/s. By lowering the sampling rate, MPEG-2 layer III removes all frequencies above half the new sampling rate that may have been present in the source audio.  As shown in these two tables, 14 selected bit rates

Ancillary data.

The ancillary data field can be used to store user defined data. The ancillary data is optional and the number of bits available is not explicitly given.

Metadata.

A "tag" in an audio file is a section of the file that contains metadata such as the title, artist, album, track number or other information about the file's contents. The MP3 standards do not define tag formats for MP3 files, nor is there a standard container format that would support metadata and obviate the need for tags. However, several "de facto" standards for tag formats exist. As of 2010, the most widespread are ID3v1 and ID3v2, and the more recently introduced APEv2. These tags are

Licensing, ownership, and legislation.

The basic MP3 decoding and encoding technology is patent-free in the European Union, all patents having expired there by 2012 at the latest. In the United States, the technology became substantially patent-free on 16 April 2017 (see below). MP3 patents expired in the US between 2007 and 2017. In the past, many organizations have claimed ownership of patents related to MP3 decoding or encoding. These claims led to a number of legal threats and actions from a variety of sources. As a result, uncertainty about which patents must have been licensed in order to create MP3 products without committing patent infringement in countries that allow software patents was a common feature of the early stages of adoption of the technology.  The initial near-complete MPEG-1 standard (parts 1, 2 and 3) was publicly available on 6 December 1991 as ISO CD 11172. In most countries, patents cannot be filed after prior art has been made public, and patents expire 20 years after the initial filing date, which can be up to 12 months later for filings in other countries. As a result, patents required to implement MP3 expired in most countries by December 2012, 21 years after the publication of ISO CD 11172.  An exception is the United States, where patents in force but filed prior to 8 June 1995 expire after the later of 17 years from the issue date or 20 years from the priority date. A lengthy patent prosecution process may result in a patent issuing much later than normally expected (see submarine patents). The various MP3-related patents expired on dates ranging from 2007 to 2017 in the United States. Patents for anything disclosed in ISO CD 11172 filed a year or more after its publication are questionable. If only the known MP3 patents filed by December 1992 are considered, then MP3 decoding has been patent-free in the US since 22 September 2015, when, which had a PCT filing in October 1992, expired. If the longest-running patent mentioned in the aforementioned references is taken as a measure, then the MP3 technology became patent-free in the United States on 16 April 2017, when, held and administered by

Alternative technologies.

Other lossy formats exist. Among these, Advanced Audio Coding (AAC) is the most widely used, and was designed to be the successor to MP3. There also exist other lossy formats such as mp3PRO and MP2. They are members of the same technological family as MP3 and depend on roughly similar psychoacoustic models and MDCT algorithms. Whereas MP3 uses a hybrid coding approach that is part MDCT and part FFT, AAC is purely MDCT, significantly improving compression efficiency. Many of the basic patents underlying these formats are held by Fraunhofer Society, Alcatel-Lucent, Thomson Consumer Electronics, Bell, Dolby, LG Electronics, NEC, NTT Docomo, Panasonic, Sony Corporation, ETRI, JVC Kenwood, Philips, Microsoft, and NTT.  There are also open compression formats like Opus and Vorbis that are available free of charge and without any known patent restrictions. Some of the newer audio compression formats, such as AAC, WMA Pro and Vorbis, are free of some limitations inherent to the MP3 format that cannot be overcome by any MP3 encoder.  Besides lossy compression methods, lossless formats are a significant alternative to MP3 because they provide unaltered audio content, though with an increased file size compared to lossy compression. Lossless formats include FLAC (Free Lossless Audio Codec), Apple Lossless and many others.

MP3 (formally MPEG-1 Audio Layer III or MPEG-2 Audio Layer III) is a coding format for digital audio. Originally defined as the third audio format of the MPEG-1 standard, it was retained and further extended—defining additional bit-rates and support for more audio channels—as the third audio format of the subsequent MPEG-2 standard. A third version, known as MPEG 2.5—extended to better support lower bit rates—is commonly implemented, but is not a recognized standard.

动态图像专家组-1或动态图像专家组-2 音频层III(),常简称为MP3,是当今流行的一种数字音频编码和有损压缩格式,它被设计来大幅降低音频数据量,通过舍弃PCM音讯资料中对人类听觉不重要的部分,达成压缩成较小档案的目的。而对于大多数用户的听觉感受来说,MP3的音质与最初的不压缩音频相比没有明显的下降。它是在1991年,由位于德国埃尔朗根的研究组织弗劳恩霍夫协会的一组工程师发明和标准化的。MP3的普及,曾对音乐产业造成冲击与影响。