i use max/msp. i've been using it off and on for years and have only scratched the surface. essentially they make a piece of modular software called a "patch" - that generates music with samples the've defined, and edits them according to rules they've defined. Chances are some of the patches are also generating sound as well (synthesized drums, etc).
Confield specifically was (im pretty sure mostly if not all) generative music. If you're interested in generative music, then I suggest "The Computer Music Tutorial" by Curtis Roads.
Roads, the inventor of granular synthesis, has written many interesting books, but this one in particular, covers everything there is to know about computer-based music and dsp. It's the most thorough book on the subject, but it's out of print afaik. maybe you could "find" a pdf on the internet - but the book itself (which I'm proud to say I own) has an extensive chapter on generative music and the theories behind it (the book itself is around 5 inches thick).
here's some dope places to start if you're really interested in algorithmic composition:
Wikipedia! Yay!
Markov Chains
http://www.cycling74.com - they make max/msp/jitter/gen/mira etc. you can get a free 30 day trial of max if you really want. Learning max feels like this
every 15 minutes, for days on end. once you break through one wall, you can always be sure theres another one waiting right behind the previous rubble.
Back to confield - the max patches they made were most likely probabilistic sequencers based on markov chains - I've not had the guts to delve into this shit yet - but I'll tell you, if math(s) teachers showed you how dope math can be by playing Autechre - we'd have a lot more math geeks out there - and I wouldn't be teaching myself calculus now
