The Auduino project turns Arduino into a PWM based sound synthesizer –
Sound is generated by playing the same noise (‘grain’) repeatedly at very high speed. This merges into a tone that is an audible hybrid of the repetition rate and the original grain.
The grain consists of two triangular waves of adjustable frequency, and adjustable decay rate. The repetition rate is set by another control.
Only basic hardware required – 5 potentiometers, and an output jack –
Looks like a cool project – details, links to Arduino code here – Auduino