I dont know if you took the time to check this out but where to old BGM files were there are some new ones... you take a song or BGM from another game and place it in there as long as the name is the same.
I know we could always do this... Notice the Word "NEW" BGM
there were only 2 before... I knew when the game came out. Remember that this is in game BGM so it plays during Fireteam. Read the post twice if you have to before reply. Thank You.