Midi
MuseNet
Musenet takes an "intro" and then "evolves" it with AI in different styles such as Beatles, Mozart or Bluegrass. Interestingly you can upload your own custom midi track and let it evolve that too.
I tried adding a file created by Computoser as a starting point, and I think it made it more Beatles-y but it's hard to tell. Doesn't have a download option.
Mindful Harmony
A tool to compose or arrange unusual chords - and you can then save it in midi (maybe importing it into Garageband or BespokeSynth).
