Uh, kinda hard. I did that music mod mainly because I thought that I had nearby sources, and since it's only one culture, it was fairly easy. But for a full game, I don't know, I would have to ask for a lot of permissions to use music files from other mod teams. Possible, but I can't give you many original things.
Sentence Deleted. No mentioning potential copyright infringement - sorry! (Jubal)