I was looking at the music file and I think you can just copy and paste and then specify Egypt etc to use it.
I think the game searches the header and activates with a pacticular faction is mentioned.
So instead of have all the eastern egypt carthage etc all LUMPED together you can have each one having unique music. I havent tried this, but maybe some one would give it a shot.
Just dont forget to delete the events.dat file first. lol
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