Microsoft sells the rights of the music in the Halo & Halo 2 games to warner bros. Not only Halo but also few others like Age of Empires, Fable, Kameo. They have also had an agreement on Halo 3 too. I wonder why did they brought though, but the music really is one of the i have ever heard.

Though the agreement has done, they didn’t reveal the financial terms. Warner/Chappell Music, the publishing arm of Warner Music Group Corp. will claim and register Microsoft-owned copyrights in all territories worldwide.