An acomplished programmer as well, Gustavo Díaz-Jerez is author of FractMus, a windows program that explores algorithmic/generative composition using algorithms derived from number theory, non-linear equations, cellular automata, and fractals. FractMus saves midi files that can be later processed in other software for further exploration. He has written a number of articles on the subject that have been published by prestigious publications such as Electronic Musician. A short, introductory article on fractal music can be found in Musikene's magazine Ahaire Nº 4 (in spanish). You may also get it here. His Manhattan School of Music Doctoral Dissertation Algorithmic Music: Using Mathematical Models in Music Composition also serves as a good start if you are interested in the subject.