I found this one on Youtube:

http://www.youtube.com/watch?v=N-bVd9t2XA0

This is probably the Cataclysm loading screen music, it's long and got many WoW music's mixed into.

(Vanilla loading screen music, Bc Loading screen music, Wotlk loading screen music, Invincible "song", ToC Theme, Gunship Battle Music, Ulduar Antechamber Music)

That's the those i recognized, if it's old news i apologize for stealing your time.