Mathematics of music is a frequent guest topic of John Baez's This Weeks Finds in Mathematical Physics. Week #234 was one of the most interesting, referencing lots of work, including Tymoczko's : http://math.ucr.edu/home/baez/week234.html Many books are mentioned there already, but I would like to add one more, Benson's "Music : A Mathematical Offering", which is a little lighter read (at least not going into category theory stuff), downloadable here : http://www.maths.abdn.ac.uk/~bensondj/html/maths-music.html
WHOA, as a CS/Music Theory major and as an FP hacker, I must say, this is mindblowing stuff that I've definitely thought about but never implemented. Props to this guy. Good next steps after these would be notations for tonal, contrapuntal and schenkerian analytical structures, not to mention some sort of interface to, say, something like pd (puredata.info). Good find.