Kumikyoku Nico Nico Douga

Kumikyoku Nico Nico Douga (組曲『ニコニコ動画』, Kumikyoku "Nikoniko Dōga"^?, lit. "Suite: 'Smile Video'") is the name of a series of video medleys, and is also the title of one of the videos in the series. The original video was created by Shimo (しも), a user of the popular video sharing site Nico Nico Douga.

Kumikyoku Nico Nico Douga was first uploaded at 5 June 2007 with the title 「Nico Nico Douga中毒の方へ贈る一曲」 and continued to be worked on. A second version was uploaded on 23 June. The number of views skyrocketed to over 1.8 million after little more than 2 months. From July to August in 2007, the video maintained first position in number of views, with over 3.3 million comments, and was in over 100,000 mylists at the height of its popularity. Its popularity was thanks in part to subsequent videos.

5 days after the original video was uploaded, another user uploaded a version with his own singing. After that, many users began to upload spin-offs (such as the play version, dance version) of the original video. Some of the lyrics from the original songs were improvised or mondegreen were used instead. Users sometime compile multiple user versions of the medley to form a 'chorus' video. Most of these "auditory illusions" were already well-known/prevalent on Nico Nico Douga.

The videos attracted a lot of singers who would add their own vocals to karaoke versions of the songs, the number of such videos far exceeded that of earlier videos.

It's often misunderstood that the title "Kumikyoku" (組曲, lit. musical suite, or music selection^?) is not a "music selection" in a strict sense, only "Nico Nico Douga medley songs used in it".

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Wikipedia