I have a very weak grasp of music theory and write a lot of music generators based on that weak grasp. They are mostly successful, compared to my prose generators.

It's not so much that I'm overestimating music theory, but that the state of really concrete analytic structures in other arts (in terms of being well-positioned to produce new works from PRNG output) is pretty bad.

It's pretty straightforward to construct a program that produces mediocre music that really resembles human-written mediocre music. Computers are also really good at producing poetry that is indistinguishable from the work of mediocre human poets. Computers are not good at producing images that look like they were hand-drawn by a 12 year old Deviantart user or producing stories that read like they were taken from fanfiction.net