@vincentoliver here the fix was not to rely on fmod for that part, as in quantized volume change. i found a different work around.
for my purpose, i ended up creating a way to layout music and the ‘quantized change’ was not in volume but of layer. that worked out for my purposes.
let me know if you need more info or what’s your specific context and i can try to unearth that project and/or give you some tips.