Servovalve.org is offering two nice stand-alone applications: Semuta, a soundscape machine that can be automated and Marteleur, a type of drum machine which is split up into 2 synchronized tracks.
Both applications come with sounds which can be modified or replaced by your own. I don’t really know what all the controls do, and there isn’t much help available so just go experiment!
There is no option to save audio from Semuta or Marteleur so if you want to keep your results you’ll need to record it with some hardware or use audio capture software.
Semuta and Marteleur are offered in Mac OSX and PC format and can be downloaded from Servovalve.org
More information: Servovalve