James Patten and Ben Recht from the Tangible Media Group at MIT developed Audiopad, a live music composing system that is a projected interface over a tabletop. it uses little plastic shapes (aka "pucks") as knobs - its position tracked by radio sensors - to graphically control the preprogrammed rhythm, bass line, melody, microphone, etc. other fun projects from the tangible group are: Lumitouch, topobo. another interesting "mixing machine" is the DJ I, Robot.