There already was a post about this a while back, since then I did a lot of testing.

I have an idea as of how this supposed to work, some music elements only play under certain main themes and such, but it's still chaotic.

The main problem is that there is no preview, and as I'm trying to create a trigger "library" of the available working music resources, I'm constantly running into inconsistencies, files that played before don't play anymore, or play something entirely different. Even Explore_ ones that I assume supposed to be the base ones.
(if I'd want to take a wild guess, I'd say there is a lot more going on behind the music triggers, for instance the system witch determines how certain theme elements should be run, and under witch main themes, and at least in the editor this thing is invisible, and pretty messed up. It does random stuff, or effect other triggers if they are being run after one another. Like some Explore_ ones will play whatever main theme was played before, or nothing at all.. )

It is really messy, and I can't for the life of me find any other way of figuring out what's what. Gm_ stuff doesn't work in the editor either so I can't even use the gm mode for previews. I tried unpacking sound files, but since they have numeric codes instead of names, that wouldn't help either even if I had them converted to something I can actually play.