Part 1: File Structure
Image tutorial courtesy of @DemonicDax
Part 2: Track IDs
Updated list compiled by @budadeth and @cyanfire
All you gotta do is name the music file after the track ID that it's supposed to replace. (example: vermillion city is 313, so if you want to have All Star by smash Mouth play in verm, you have to name it 313.mp3)
And then drop it in the folder of its corresponding region.
If an ID is missing from this list,