I realized recently that arm7/audio.h it's missing a way to access audio channels 'volume divisor' (bit 8 and 9 here) directly, without affecting other parameters.
So I think maybe it's possible to add
Code: Select all
#define SCHANNEL_VOL_DIV(n) (*(vu8*)(0x04000401 + ((n)<<4)))
My 2 cents.