This is a higher quality video of the robot.
There is more description of this project at Let's Make Robots site : http://letsmakerobots.com/node/32455#comment-85128
Frits Lyneborg first described the project on the LMR website, which he hosts. He also wrote an in-depth article in Make magazine volume #27. My version has adapted his BASIC code for a Pic microprocessor to run on an Arduino clone.
The robot has a PING sonar sensor, a CDS photocell, and a ZX-Sound Board I built from scratch as inputs. Based on the inputs, the robot plays different "songs" which are in the code.
Frits used rather expensive geared pager motors from Solarbotics. I used solenoids from a surplus company instead. They are much cheaper, but need a powerful battery to drive them.