I'm guessing, you know which sounds belong to which category..
So in the play audio action (which you would have to make for each sound anyway) you could assign the right variable to the right sound..
If you want to affect sounds already playing, adding the tag "Music", "Ambience", etcetera to the play action, should work..
Then you can reference those in your event-sheet to set the volume..
Could be, I'm completely missing the point of your question, though..