I agree with the legend, Audiotrack. It would be nice to have as a list in Stylepicker, too.
To add to your list..
- M_(name) are styles containing a MIDI Supertrack
- C!(name) and C_(name) are usually refer to country MIDI styles
- J!(name) and J_(name) are usually jazz MIDI styles
- L_(name) are usually Latin MIDI styles
- NR_(name) are Nashville Rock MIDI styles
- ZZ(name) styles are built-in BIAB MIDI styles
While I'm not sure what -(name) means, I think it might mean that a style is based on a parent style.
As an aside... There are some styles that begin with _(name) that have MIDI tracks and some that being with =(name) that have MIDI Supertracks. I suspect that these instances are wrongly named tracks.