That function generally does nothing.
If you want to balance the music and sound effects, there are feature adjustments for them.
How they work is based on attenuation, so if you want the music or sounds louder you set them to a larger negative amount (kinda counter-intuituve). If you want music or sounds quieter than default, input a + number.
Either way, play around and find a good balance with what works for you.
On Metallica, I have it set as follows for louder music (2x louder) and quieter sound effects/callouts:
Feature adjustment #124 - Music Attenuation = -20
Feature adjustment #125 - Speech Attenuation = -10
