It'll sound like programmed melodies
How will it work (well, it does already work on my computer ... and I'll put some alpha code for people to play with up on the web site in a few days). MMA will need a pattern description (much like the other patterns it uses). From this it will pick out notes depending on the scale/chord in the piece.
Honestly, I'm not a big fan of most of the electronic/computer music I've encountered over the years. But, I'm doing this addition anyway ... silly? Not really, there are times when I think this feature will be quite handy:
1. MMA will be able to create a melody based on chord progressions. This can be a real aid to people learning how to improvise to compose. I doubt that the output will ever put a real composer out of business!!
2. Even more helpful, in my blurred vision, is using this feature to generate short fills to be used in repeat bars, intros, endings. Since most of the bits and pieces of the new feature build on existing track/pattern stuff, it should be fairly seamless to include this in your song files.
So, stay tuned