==> ARDUTOUCH KITS ARE FINALLY AVAILABLE. <== ArduTouch is an Arduino-compatible music synthesizer kit. Build it, and it works! Way low cost (target price per kit is $25 -- currently $30.) It comes with a pre-programmed music synthesizer that makes way cool sounds and music and noise. An ArduTouch Arduino library is available for programming in more super nice synthesizer features. The Library comes with many way cool example synthesizer sketches that also serve as a tutorial for making your own ArduTouch synthesizers (which are Arduino sketches). For those who want to learn more, the documentation teaches the basics of Digital Signal Processing for audio generation (more documentation coming soon).
http://cornfieldelectronics.com/cfe/products/buy.php?productId=synth