Wow. This is the coolest thing I've seen in a while. And talk about a "junkbot," it's made from scraps of wood, a cheese container, tons of hot glue, some gearmotors, the Picaxe 28, and the L293D motor driver. And that's a knitting needle as one of the drumsticks.
Yellow Drum Machine
http://blog.makezine.com/archive/2008/03/mobile_drum_robot.html