I think only @StepS7578 may be able to answer this!
I have noticed within my Original Voices Mod that - although I have managed to change the voicovers in the intro and outtro scenes, there are background SFX and music that are still present.
Does anybody know if these can be modded over (a blank .wem file ususally does the trick) - the only problem is I’m not sure what the filepath or name needs to be.
EDIT: Turns out the answer was pretty simple, it’s just the usual campaign intro/outtro names with “_SFX” and “_M” suffixes! I now have the BGM and SFX successfully muted!