These are probably > 2 channel files. While I've seen them and it is probably straightforward to extract, I haven't written anything to do it yet. FastElbja, have you?
Prime Blue: The music seems to be pretty good, but I am curious as to how Bowser's Castle sounds. Rainbow Road is alright, maybe not as good as in 64 and Double Dash. Award Ceremony is a remix of the 64 and Super Circuit version.