I have a question as well about this. Loops are something you could do in a program like audacity right? Just loop a BGM and import?
And check this out... for a "specific trainer" or "trainertype" I found this on the Wiki. Go to the wiki then go to defining a trainer.
If you look at line 7. There is ME that should play before the battle, but it doesn't seem to happen. Does anybody have an explanation? I edited it in the trainertypes text file, but it doesn't want to work for me.
The Intro-ME function is bugged. It only works reliably with .mp3 files.