Arduino Theremin
Arduinos are truly universal, this one is playing some fine music, almost makes you feel like dancing, doesn't it?
http://www.youtube.com/watch?v=fX9eUR5EXOA
Used code and schematic from this site:
http://interface.khm.de/index.php/lab/experiments/theremin-as-a-capacitive-sensing-device/
Arrrr...duino!