A photo-sensitive electronic instrument that includes 2 potentiometers to generate various sounds.
Its kind of an implementation of a theremin. Part count seems minimal with two resistors( 1K and 10K ohm), a CDS cell and an 8ohm speaker. The variable resistors connected to the ADC help generate dutycycles to drive the speaker. You can hear a preview of the range of sounds that the setup can generate here. While you are at it, make sure to check out his updated MSPhere documentation. Code is available on his blog page.