I remember someone over at Gamingforce had ripped the versions of the songs out of the game since they're still slightly different than the originals (some better, some worse, IMHO), but since our forums crashed last week and when they're coming back up is a little questionable I don't know if you'd have much luck searching there for it.
All I can tell you is there is someone that ripped it out there somewhere (this for GH1, though he probably did it for 2 as well).