I didn't realize Music Pan and Music Pan Transitions were actually ever used. This will be reinstated with The Audio Replacement. Looking at the field code in Makou, it seems it uses 2 byte values this time, rather than one. So Left is 0, centre is 0x4000, and right is 0x7FFF. Effect balance is 0, 0x40, 7F. Unless Akao2 causes some sort of mess... but I doubt it.
Also seems that there has been a miscommunication somewhere with the sound programmer / design team / field programmers... because although akao2 should allow for 2 byte time values, as I said previously this isn't the case with the hard code, which has accidentally left only one byte being used. I am still not sure if this is the case in PSX, but I'll be testing soon. Some of the field programmers have kept to a one byte maximum value for time intervals in field (indicating they've been told that's the limit)... but not in cos_btm2 for example... where you'll find a music transition of 500. If the akao wrapper is broken in PSX, this fade will be totally broken too.