Hey,
I left this alone for a little while but have come back and still trying to figure it out. What exactly do you mean by master sound class?
I have created a Sound Mix (https://we.tl/1KIrKvUo2t) which should set the volume to 0. In BP, if I push this sound mix, it doesn’t do anything to effect the volume.
The only place in the Sound Mix I can see you can change the volume is if you add a Sound Class Effect, where you can change the Volume Adjuster to 0. But I can’t see anything about it affecting a ‘master sound class’.
What am I doing wrong?