This is turning out to be harder than expected. They store sound effect volumes separately for menu sounds, world sounds, weather and background music, which is cool, because it means we can add an option to have them all at different volumes. The problem is, I cannot for the life of me figure out how the weather sound volume is controlled internally... I'm still looking into it, just to let you know it's quite a bit harder than I was anticipating.
oh dang! well, i primarily just want to use something like this to turn on and off bgm quickly so i can play my music when i'm doing monotonous things but turn it back on quickly when i enter or am about to enter a cutscene, so just something as simple as controller bgm volume would be awesome. good luck tho! hopefully some kind and knowledgeable folks come along to help, i would if i could x_x