Is there a way to change the music tracks in this?

No, this isn`t a dodgy 1st poster thread about DVDs...

I`m wondering if there`s an option in Civ5 that lets you choose a music folder and for the game to play custom tracks from it. i`m sure there was... Can`t seem to find it.

Or maybe that was Civ4...?

You can't add custom music to the game. That'll be available in the Fall Patch