Is there a way to turn off the BGM in games?

[Shonumi]

Technically, the Zelda ucode differentiates between music and sound effects, so it would be possible to hack Dolphin's HLE implementation to produce silence for the relevant samples. A potentially buggier method would be to set the status of a sound as "Off" whenever the ucode indicates the sound being processed is music. There aren't a lot of Zelda ucode games, in comparison to AX ucode games though.