The sound comes from The Intense Voice of Hatsune Miku, a Vocaloid song showcased in a Project DIVA F 2nd promotional video and known for pushing Miku's synthetic voice to an extreme tempo. Hatsune Miku is a virtual singer whose fast, clear delivery made the track a standout example of machine singing. Online, Spanish language titles comparing her speed to Eminem helped turn the excerpt into a shareable joke about impossible rapping. It remains popular in anime edits because few human performances can match its pace.