I just wanted to give a huge thanks to Marty O'Donnell because his music is just too brilliant. Apart from the Halo main themes and the popular music everything he makes is just as perfect for the situation as can be. For ODST and Reach he made an entirely different sound but somehow kept the feeling that it was Halo.
For me the driving forces for me to continue to play Halo are about 30% nostalgia 30% game play and about 40% music, the music lends to the nostalgia too.
I heard Marty say in a video one time that the goal for music is to provoke emotions without people knowing it. And i'm well aware that that's the purpose of it and that is just fine by me.
Not that the rest of Bungie isn't brilliant as well but the music just stays with me.