Also they would fade out for cutscenes and fade back in afterwards and whatnot. That was some amazing MS-enforced implementation we’ll probably never see again.
When I was a lot younger I would combine the stereo a/v cables from a game console with the stereo a/v cables from my CD player using an RCA splitter as a combiner into a receiver and play stuff like Doom64 with Beethoven’s 9th in the background.