A. Gelfand (any relation to I. Gelfand or S. Gelfand?) has written a pair of stories for Seed and Wired concerning R. Mahanthappa and his new cryptologically inspired album, Codebook. I highly recommend that you give it a listen; between Gelfand's articles, the label's site for the recording, and the artist's myspace page you can listen to most of the numbers on the CD.
I really appreciate his approach to mathematical composition. He describes his initial cipher of J. Coltrane's "Giant Steps" as "unplayable", specifically wishing to avoid "the appearance of random noise." Rather than leave the melody of "Frontburner" in its raw encrypted state, Mahanthappa "had to tweak his coded message until it could be classified as music."
Perhaps it's an overstatement to assert that it wasn't music before the "tweaks", but I'm sure that it's much better music on their account. It's refreshing to see serial elements used as a stimulus for creative expression rather than a programmatic straitjacket.