This is how you can change the title music to whatever you want.
Before you bother to read the rest, make sure you have MyWarcraftStudio.
I also suggest you extract everything thats related to the title screen from your MPQs, I downloaded an MPQ to make it the BC background so I already have it. It removes the ESRB stuff so you don't have to.
DL Link of it: http://www.mmowned.com/forums/simple...ackground.html.
Boot up MyWarcraftStudio and open the patch you downloaded via Edit MPQ Archive at the Pack tab in MyWarcraftStudio, or just press P and click Edit MPQ Archive and open your MPQ.
Now go to the mp3 you want to make it, for example, I will make it the Unreal Gold theme and rename it "WotLK_main_title". Now go the the Pack tab in MyWarcraftStudio again and click "Add file to archive.". Make it so it says "Sound\Music\GlueScreenMusic\WotLK_main_title.mp3" so it ends up in the folder. Don't forget to delete the original mp3 when you do it and when it says an error, ignore it and add the Sound\Music thing in there. After all of that work, save and close the MPQ and MWCS, and now open up the game. It should work now!
Have fun!