MUTE_AUDIO_ON_FOCUS_LOST only affects music, not sounds

[AdamPlenty]

I don't know whether it's a problem with the setting or with something on my system (what it could be, I've no idea), but this only affects the music for me. The sound is always muted when the window loses focus, regardless of this setting.

[eddebaby]

This is a "bug" in the Miles Sound System library. It is the same way in DK too (e.g. keepd3d via DxWnd). You can fix the described issue by using v3.6f of MSS32.DLL. You can get this version of the library from the vogons archive on github or alternatively from the Commandos: Behind Enemy Lines Demo.

Presuming all sound will eventually be moved to SDL, this MSS issue will then become redundant.