The ODST mythic disc has a different song and I think it's a lot better IMO. I wonder why they didn't go with it for the default disc.
[url=http://www.youtube.com/watch?feature=player_detailpage&v=-5gIu7o6UUE#t=87s]Mythic disc song[/url]
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I'd think because having the same menu music would be boring. I think the music on the Mythic disk is much awesomer though.