Wow. It turns out that my little adventure-evening (described below) involved an argument with none other than Douglas Hofstadter, writer of the Pulitzer Prize-winning, subversively influential Gödel, Escher, Bach: an Eternal Golden Braid. If I'd realized who he was fully, I probably would have been a bit more respectful! But for any who are interested, his thoughts are essentially as follows: Sounds Like Bach. (I know I described our discussion below, but only very briefly - this article gives much more of the sense of how he comes across.)
The program he refers to, EMI, is written by David Cope, and has some sample mp3s online, which can be found here.
To me, the fake-Chopin lacks dramatic direction (through a lack of structural coherence), and the fake-Bach and fake-Beethoven are nearly-prosecutable ripoffs of Bach's F-major invention and Beethoven's Sonata Quasi Una Fantasia, well known as the Moonlight Sonata. As Nate explained (he's heard a lecture by Cope), this is largely because the program takes apart and reassembles. It goes through a set of actions that could be undertaken by any human, with the end product of a piece with lots of stylistic similarities to the model. While I think the program is incredible - it certainly writes stuff a hell of a lot better than my students - I still take issue with Hofstadter's sci-fi doomsaying (Computers will render us obsolete!), Pulitzer Prize or no, and think that the incredible in "great" music may be a bit more ineffable than he thinks. (I wanted to encourage him to take a class in Schenkerian analysis with Prof. Samarotto - a man equally as weird and and perhaps more so than Hofstadter - and see what he said then, but I was afraid of sounding too pompous. I'm glad now that I refrained...)