Nice work! Music21 is an awesome library.
I'm integrating toolkits for spectral composition, constraint programming, parrallel motion detectors, genetic algorithms, cellular automatons, etc.
Here are other stuff I've done with it:
Mozart's musical dice game (waltz): http://www.scripthica.com/5708118910566400
first 10,000 digits of pi: http://www.scripthica.com/5680051299287040
Machaut's Ma fin est mon commencement: http://www.scripthica.com/5135440856219648
Riley's IN C: http://www.scripthica.com/5672565171290112
The 'cool' thing about this software, is that you can share algorithms that generate compositions. it's also going to be open source as soon as I finish with phase 1 of the project.