Global Volume

I've started working on the options menu for my game, including volume settings, starting with the global one.

There is either an issue with this, or maybe a misconception on my part?

As an example, I set the global volume to zero. Immediately all sound, music & speech in the current scene are muted,
as you would expect.

However, as soon as any sound is played or a character speaks as the scene progresses, volume is automatically unmuted & sound, background music & speech are resumed.

I can obviously get around it by setting sound, music & speech volumes separately, but that begs the question of the value of a global setting in the first place.

Maybe a bug? The global volume table is supposed to control the master volume channel, as far as I'm aware.

Could be ... I find the way sound/music has been implemented a bit odd... for instance if you start playing some background music at volume 20, then this seems to set a maximum level for all music after this point.

After doing this, if you set the music volume to 100, it still only plays at level 20, but if you set it to 50, as far as I can ascertain it plays at half the level 20 volume.
If the current character exits this scene & goes into one where new background music is set in the scene properties at level 100, it will still only play at level 20 maximum until the game is restarted.

So what I have to do is remember when starting to play or change background music to start playing it at level 100, then immediately issue another set music volume to play it at the required level, or else the volume level of all other music is affected.