Greetings: Tech Support replied with this response:
"When you change the Master volume using the Conductor, it is the same as changing the "Combo" volume in the main screen of Band-in-a-Box. If you change the volume on Combo, you'll notice that it changes the volume of all the individual tracks to what you've set for Combo, and they're suddenly all the same. It's weird, but I've asked one of the programmers, and it's not a bug, it's just how Band-in-a-Box is designed to work."
- PG Music Support

My Observations:
As of yet - there is no way possible to have a MasterVolume for all tracks and Audio track, without losing the individual volume settings for each track. For live use, one would be forced to use a volume pedal, or other hardware solution - if you wanted to keep your specific instrument volume mix, but still allowing MasterVolume change.

When you change MasterVolume:

Ctrl+Alt+A
Decrease master volume by 5.

Ctrl+Alt+S
Increase master volume by 5.

This does change MasterVolume, but sets all individual tracks to the same level, so you would lose the balance of a specific mix. i.e. - If RealTracks: Bass=40, and Drums=55 - after changing MasterVolume Bass and Drums would be reset to equal volumes - and the Audio track volume would not change at all.

WishList: A global MasterVolume for all RealTracks and the Audio track, controllable by hotkeys that did not lose the individual track balance.