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, she/he 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.