Wolfram Tones (http://tones.wolfram.com/).

WolframTones works by taking simple programs from Wolfram’s computational universe, and using music theory and Mathematica algorithms to render them as music. Each program in effect defines a virtual world, with its own special story–and WolframTones captures it as a musical composition.

Essentially, it’s a way of creating nice, short bits of colourful soundworlds. And there’s a mobile version too allowing you to create ringtones!