Can it support multiple instruments?

I think people that are interested in procedural music generation might be interested in a program called Band-in-a-Box, particularly if you want to generate popular music (jazz, blues, rock & roll, pop...). It's a complicated GUI with too many bells and whistles for my taste (and quite a few bugs), but it's easy to use to generate a very convincing rhythm section for a tune, given the chord changes. There are many different packages including different sets of instruments and styles. The so-called RealTracks are particularly good, and I think are worth mentioning in this thread because they generate music in a much different form than what has been described so far. They basically recorded some musicians for hours playing over common chord changes, divided the performance into phrases and the software will put together a whole track by pasting together these phrases, trying to match the chords in the recording with those in your tune. The results are not easy to distinguish from a real band performance. You can also add soloist tracks, but I find them less convincing.

I probably should have mentioned this approach earlier, but I somehow forgot about this piece of software when I wrote my first post in this thread.

Can it support multiple instruments?

i supose it could in a way. If you parsed through the melody, then used the same random seed for the harmony and parsed it separately. then gave them both the same random seed when producing the output, it 'may' align. I have not tested this though. While the first bar or two may align,i would expect them to diverge eventually, though controlling the random seed may help.

Hi,
I don't mean to zombie and old thread but I wanted to share my experiments with procedural song generation.
My technique is different from a HMM. I use a dynamic hierarchy method and allow each instrument to apply a small influence to the others in terms of energy.
You can listen to samples Here
Everything is dynamically generated at once. If anyone is curious I give more details about how the program is structured.