There are 3 - one is an original work by hazza, one is a shortened version of it, and one is The Ecstasy of Gold (acoustic) by John S.
You can find hazza's work at
www.hmorton.net once it's finished again.
All three tracks are in mp3 format in
sourcemods\FortressForever\sound\ui\ as
gamestartup(0-2).mp3.