Boom! Decompilable after all. And look what that made us finally point
out: In all 4 games that use this function, its return value is
undefined if BGM is inactive. (That is, if the user disabled it, or if
no FM sound board is installed.)
Part of P0148, funded by [Anonymous].
4 games, 4 different versions of this function. Interestingly,
moving the game-specific differences to inline functions makes it
obvious that this function was only intended for BGM, not sound
effects.
Part of P0139, funded by [Anonymous].
nmlgc