One is that real music composition is never done where the timbres are separated from the composition. Classically notated music looks kind of like this, but it's really just a shorthand. A composer knows intimately the sounds she is working with.
For pop music, the timbre itself is a mode of creative expression. Innovation in musical timbres and sounds is an expected part of pop music. (I'm using "pop" in the most general sense, covering a large amount of contemporary genres). The meaning of the music is not captured by simplistic reference to musical notation concepts.
The other major limitation of generated music, to my ears, is that of overall compositional structure. The units of composition usually are short, and only locally referenced. So the compositions lack interesting shape over the course of time.
If you think of a composition as a story, it's as if a bunch of plausible paragraph that are coherent within them selves are strung together with only loose reference to each other. So a longer "plot" doesn't emerge.
It's true that composers almost always have a sound in mind when they write the notes, but it's very common to perform compositions using entirely different instrumentation to that originally envisaged.
Hopefully they keep improving until they make the best human composers look mediocre, despite being millions of times faster. Unbounded amounts of new high quality low cost music? Yes please.
A paper: http://ncra.ucd.ie/papers/gecco2011_jmcdermott.pdf
Some short mp3s: http://www.skynet.ie/~jmmcd/software/GraphMusicDemoPieces.tg...
Longer, slow-developing stuff on soundcloud (using slightly different software): http://soundcloud.com/jmmcd/tomorrow-is-a-new-day
One problem I noticed sometimes was a limit to Garageband's polyphony in the pianos. I think it only allows 8 or 10 notes at a time in some cases (not sure exactly how it works) and my software has a habit of playing a lot more than that.
from imaginary_music_module import piano_performer as p
That would be nice :)
It makes the mistake of trying to generate in established genres. None of the genres I care for were anywhere near the mark.
Sadly his code (lisp if I remember correctly) isn't on github either...
still, a little too random
since it's algoritmic, maybe you can go for a little "coherence" throughout a piece, if it makes sense?