I'm not an audio person, but if the component tracks (sublayers, like audio, vocals, guitar) of a song were separate, it seems like a reasonable use. People could fork songs with different vocals, combine different parts of songs for mashups, etc.
edit: As an aside, as an artistic statement on why autotune is terrible, I was thinking it would be interesting if someone would show the world what classic songs, ruined by autotune, would sound like.