Nightcore

A nightcore edit is a version of a track that increases the pitch and speeds up the pace of its source material by 10–35%. This gives an effect similar to playing a 33.3 RPM vinyl record at 45 RPM. The name is derived from Nightcore, a Norwegian duo who released pitch-shifted versions of trance and eurodance songs, but now more broadly refers to any sped-up cover. Nightcore is also commonly associated with anime and sometimes internet "Weeaboo" culture, with many YouTube thumbnails of nightcore remixes, containing anime characters and art. Some may also come with an audio visualiser although this is relatively uncommon
2000s: Origins.
The nightcore term was first used in 2001 as the name for a school project by Norwegian DJ duo Thomas S. Nilsen and Steffen Ojala Søderholm, known by their stage names as DJ TNT and DJ SOS respectively. The name Nightcore means "we are the core of the night, so you'll dance all night long", stated in their website named "Nightcore is Hardcore". The two were influenced by pitch-shifted vocals in German group Scooter's hardcore songs "Nessaja" and "Ramp! (The Logical Song)", stating in an interview that "There were so few of these kinds of artists, we thought that mixing music in our style would be a pleasure for us to listen to" and "Nightcore has become a style of music, a way to make the music happier – 'happy hardcore' as they say."
The duo set a template of a track in the style: a 25–30% sped-up (commonly to around 160 to 180 beats per minute) of a trance or eurodance song. The nightcore music has been compared to happy hardcore and bubblegum bass due to its fast tempos, energetic feel and high-pitched vocals. Nightcore made five albums of sped-up versions of trance recordings, including their 2002 thirteen-track debut album "Energized" and their later albums "Summer Edition 2002", "L'hiver", "Sensación" and "Caliente". Their first album was made with eJay, while all of their later work was made with what they described as "top secret" programs. All of their records were sold to their friends and DJs around their area.
Nightcore's works started appearing on services such as LimeWire in mid-2003, and YouTube in 2006. The first nightcore track to appear on the latter site was "Dam Dadi Doo" by the duo. Only two of the project's albums have surfaced on the Internet. One of the first people to distribute nightcore music on YouTube was a user going by the name Maikel631, starting in 2008. He first uploaded around 30 original tracks by Nightcore on the website. In 2009, he found a "new" nightcore track, as well as the technique to make material in the style: 
2010s: Popularity.
The first nightcore edit of a non-dance track was that of Evanescence, and uploaded on YouTube in 2011. From there, the music rose in popularity with more people applying the nightcore treatment to more non-dance genres such as pop music and hip-hop. Many of the pioneer uploaders of nightcore including Maikel631 have called these non-dance edits "fake". The nightcore scene then crossed over to SoundCloud with the help of artist lilangelboi, who had released around ten to fifteen edits on the service before being signed to Manicure Records. The head of Manicure, Tom "Ghibli" Mike, recalled, "I just got totally obsessed with it. I put up that one he did, "Light", we had him up here to DJ a few parties, and then he moved here. That was totally how nightcore became a thing for us." The label's #MANICURED playlist consisted of nightcore renditions of K-pop and electro house tracks, a few of them also incorporating production techniques outside of pitch-shifting and speeding up the source material, such as "Mile High" by Chipped Nails and Ponibbi and "Fave Hours" by F I J I.
By the mid-2010s, the nightcore scene had garnered attention from musicians such as Djemba Djemba, Maxo and Harrison, Nina Las Vegas, Ryan Hemsworth, Lido, Moistbreezy, and PC Music founders Danny L Harle and A. G. Cook. Harle and Cook have claimed nightcore to be influences in interviews, the former saying in an interview, A THUMP writer described it as the "groundwork for some of the most innovative club music today" and wrote that it also led to a number of "awful" internet memes: 
Dance Music Northwest described nightcore as "too catchy, too danceable, and far too much fun to not welcome into the dance music mainstream." David Turner of MTV described a nightcore remix of "7 Years by Lukas Graham as "the same as the normal song and plagiarism."