[Suggestion] Audio Volume Expression

Hey there. Just thought it would be really handy, especially when doing fade-in and fade-out effects to be able to get the volume of a particular tag as an expression.

Hmm... multiple sounds can use the same tag, and each can have a different volume. So in this case should it just return whichever came first or something?

Ah, good point. Maybe it should follow the precedent of "affecting the last played sound" by getting the volume of whichever came last?