Derek and Arduino

You'll find lots of helpful info in the Sparkfun Inventor's Guide.

Theremin

Theremin workshop based on: Arduino + Buzzer + Photoresistor = Home-made Theremin  by António Lopes

Drum Synth

Drum Sequencer workshop based on: The Must Build Arduino Project: The Illutron B

(The IllutronBDemo Zip file below is originally posted here and is duplicated for quicker access.)

(Click to enlarge)