possibly just get the emulator to overwrite the music section in ROM while a battle is in progress:
mars — Today at 20:06
that's kinda what I was thinking, like have the binary for the new music and import it to the rom or have mgba read it separately as if it's part of rom
whichever one is technically feasible and least annoying
how bgm vs sfx is played in game:
music patch:
possibly just get the emulator to overwrite the music section in ROM while a battle is in progress: