It would be a great idea to do ones of the following:
1) Add the option to turn the sound effects/etc off in forge; giving us the option to listen to our own music on our hardrive.
2) Give us the option to play the halo soundtrack in forge instead of going insane listening to your monitor for hours on end.
3) BETTER YET, put an item in forge (that you can only play one of) and have it trigger the Halo soundtrack (player's choice in track) to play for all players in the game. How cool would it be listening to some epic game music from the campaign when you're fending off other players in custom flood gametypes!? This could (and would) be annoying for some players; this could be countered by again, giving us control over music volume in the game options.