Thanks for your quick reply, Matt!
Great that there's a shortcut to toggle between zones, but doesn't really address my main point, which is that there's no way to synchronize two zones exactly without external hardware. Most of the time I would want the same music playing all around the house, and it would bother me if the two zones were even slightly out of sync (when walking between two zones). However, now and then (not very often), my wife or kids want to listen to something else, and then the zone concept comes in.
As it is now, if I make the bedrooms a separate zone, they can never be in sync with the rest of the place, which is no good. In fact I can't think of many situations where the current zone system would be useful without an external multi-zone switcher. I happen to have one of those already, but when I saw the "zone" menu I started dreaming of selling it on EBay! No such luck (yet).
I think it's possible to do this without interfering with non-zone users: all you need to add from a UI perspective is a tickable menu item on the zone menu saying "All zones", plus a keyboard shortcut to toggle this. That's not a big deal, but maybe programming the backend is more difficult?
Something else I just thought of - any plans of extending the zone concept to include video as well
? I'm mostly kidding - would be cool, though!
FYI, I just saw an old MJ8 bug in MC9 - I started an Audio Analysis of all 7000 tracks in my library to get the BMP happening, and left the playlist running at the same time. Worked fine for a long time, but after about 30 minutes the music playback started getting very hesitant, and finally MC9 crashed.