SSEYO Koan
Am I the last person in the world using this? Most likely.
But sometimes there is resurrection...A company in the UK named SSEYO released this amazing program many years ago. At first I didn't have much luck with it, since I was a Mac guy and it was a Windows program. Basically Koan is )or I guess I should say "was") a GUI-based program that lets you create a bunch of rules to generate music algorithmically. I think the manual says there are over 270 parameters that can be adjusted, but there are plenty of sensible defaults.
It had a brief moment of fame back in the 1990s when Brian Eno got a copy and spent a lot of time with it.
But, most amazingly, in late 2007 the Koan creators have surfaced with a new version of an algorithmic music generation software called "noatikl"!