I use Open Music too.
It's a Lisp based graphic environment.
It means that you don't have to know Lisp to use it. You just have to connect
boxes: one box takes input arguments and send the result to another box and so on...

With it you can: 
_convert midi to CSound scores
_record music on keyboard and convert to CS score
_Analyse a soundfile with Audiosculpt and convert it to CS score.
_Analyse music(midifiles or sound files)

There is a growing set of libraries including:

_Aleatoric/stochastic functions
_Chaos functions
_Constraint programing(Situation 3)
_CSound score and orc generation by Karim Hadad
_Morphology analysis
etc

I would say it's specially interesting for analysis/resynthesis of sound and music.

http://www.ircam.fr/forumnet/index.html 

-- 
Jean-Michel DARREMONT