sfxr - sound effect generator

Possibly one of the most useful application that a game developer could have. DrPetter has written a program which randomly generates a sound effect based on selected options and slider settings. The results can then be saved as .wav files, ready for use in any projects.

http://indygamer.blogspot.com/2007/1...generator.html

FlexiMusic Generator is another option which is also based off generating sounds, That's a fairly professional piece of software.