Ok I did some quick research, tell me if what I suggest here as a solution makes any sense to you
- I convert the music tracks I want in the same format you see in the screenshot
- I place them in the music directory of the mod
- I edit the txt file you see below with the proper file names and use the code that fits the track (see how the fight tracks have all the same code?)
- Based on how many tracks I added I edit the total number at the top of the file
- (The only doubt I have is what's the code behind it and how it affets the choice of the track)
Who's the guy that handles the coding of PoP? I'll try to PM him