Years ago, there was an app called RJDJ for IOS, which would modify the music it created in real time, based on user input. It was a fascinating concept. It could really useful for freestyling dance and improvised poetry, where the performer could modify a backing track in such a way that the dance, spoken word and the music are interacting in real time.

Are there any similar apps, which respond to user input at an aggregate level? Thanks in advance,