Dastgah

Dastgāh () is a musical modal system in traditional Persian art music. Persian music consists of a number of principal musical modal systems or ; in spite of 50 or more extant , theorists generally refer to a set of twelve principal ones. A is a melody type that a performer uses as the basis of an improvised piece.
Summary.
Each consists of seven basic notes, plus several variable notes used for ornamentation and modulation. Each is a certain modal variety subject to a course of development () that is determined by the pre-established order of sequences, and revolves around 365 central nuclear melodies known as (each of these melodies being a ), which musicians come to know through experience and absorption. This process of centonization is personal, and it is a tradition of great subtlety and depth. The full collection of in all is referred to as the "radif". During the meeting of "The Inter-governmental Committee for the Safeguarding of the Intangible Heritage" of the United Nations, held between 28 September – 2 October 2009 in Abu Dhabi, "radifs" were officially registered on the UNESCO List of the Intangible Cultural Heritage of Humanity.
The system has been a major influence in the "maqam" system in the Arabic music, both of which are deeply rooted in the Sassanid Persia's melodies, which entered into the Islamic world following the Arab conquest of Iran in the 7th century.
The system of twelve and has remained nearly the same as it was codified by the music masters of the nineteenth century, in particular Mîrzā Abdollāh Farāhāni (1843–1918). No new or large has been devised since that codification. When in the modern times an āvāz" or a has been developed, it has almost always been through borrowings from the extant and , rather than through unqualified invention. From this remarkable stability one may infer that the system must have achieved "canonical" status in Iran.
Terminology.
The term has often been compared to the musical mode in Western musicology, but this is inaccurate. A is usually the name of the initial mode of a piece, which the music returns to—and moreover, a identifies a group of modes grouped according to tradition. In short, a is both the collective title of a grouping of modes "and" the initial mode of each group.
According to musicians themselves, the etymology of the term is associated with "the position () of the hand () [on the neck of the instrument]". The Persian term can be translated as "system", and is then "first and foremost a collection of discrete and heterogeneous elements organized into a hierarchy that is entirely coherent though nevertheless flexible."
In conventional classifications of Persian music, Abū ʿAṭā, Daštī, Afšārī, and Bayāt-e Tork are considered sub-classes of Šur . Likewise, Bayāt-e Esfahān is a sub-class of Homāyun, reducing the number of principal to a total of seven. A sub-class in the conventional system is referred to as .
Distinguished pitches.
A is more than a set of notes, and one component of the additional structure making up each is which pitches are singled out for various musical functions. Examples include:
The Seven Dastgahs.
Most scholars divide the traditional Persian art music to seven , although some divide them into 12 (by counting Abu Ata, Dashti, Afshari, Bayat-e Kord and Bayat-e Esfahan as separate rather than subcategories of other ). Those who categorize the traditional Persian art music into seven often also list seven (, which means "songs") in conjunction with these . The following is a list of the seven and seven :
List of common Dastgah and Avaz.
"Listed in order as per the Radif of Mirza Abdollah. Flats are shown with a b, and koron (quarter flats) are shown with a p."
Less common:
Note that in some cases the sub-classes () are counted as individual , yet this contradicts technicalities in Iranian music.