Users could play a special piano that instead of playing regular piano key notes, would play short video clips of the corresponding note. So, if the user played an entire song, they would see and hear a sequence of bits of video clips that corresponded to the notes of the song. They could also share their songs with their friends.
When ID/TBWA approached me, they had the idea in place and a rough sketch. My work was to define a new art direction, design all the screens and produce the assets. I also designed part of the user experience.