This thing is absolutely awesome. After seeing this I was oddly inspired to go out and attempt to do some small systems programming. Already got myself a development board to play around with, but still missing a piece. Anyways, this little robot it pretty sweet, it uses sonar to travel a room and poll for objects that have a good resonance to them and it uses that object as a snare drum. It has a little tail behind it that it keeps rhythm with like a bass drum. It then records one loop and plays another  beat over it to make a overall nice sample. Pretty smart if you ask me! Be sure to check out the project page for the Yellow Drum Machine.