Fat Day is a band that, with their last release, included a postcard, inviting fans to write songs for them -- whatever that meant. Many did. 21 postcards were chosen, and released as a new album ("Fat Day - IV"). This is a new kind of music - before, we had Do It Yourself. Now, Do It For You. Incidentally, there's also Hamsters who will make music for you. Anybody else?
In fact, Fat Day is part of a label, Dark Beloved Cloud that relishes fan interference. Their new Singles Club has one requirement: you make 6 3" cd pieces of art, you get 6 3" cds... with somebody else's artwork.