I also noticed that there are problems with the Racing Gears Advance GSF rip.
About half the tracks are sped up - BGM #05, #08, #10, #11, #14, and #15.
Not sure whether it's the fault of the rip or the emulation in the player.
I might have contacted kode54 about this a couple of years ago on the GSF Decoder repo, but I don't remember ever getting a response. kode54, if you're reading, any chance you can look into this? TIA!
Out of curiosity, I did some research on this issue. As mentioned above, this is a rip's fault.
The problem stems from the initialization function 0x8023E20. The function accepts 1 or 2 as an argument and initializes the MusyX engine with different initialization parameters depending on the value. The first BGM is initialized with 2, but the BGM for the race in question is initialized with 1. This causes a different frequency to be set for timer 1, resulting in this unexpected playback result.
My interest is shifting to the MusyX engine rather than the playback issue, but I think I will create a modified set for this nice soundtrack when I get around to it.