How do I do A/B comparison within Ardour? Suppose I have two sub-master busses and I want to rapidly switch between monitoring one and then the other while the transport is looping. I want to switch with one control surface button or one mouse click, but the best I can manage is pressing two solo buttons on the control surface at once to toggle one on and one off.
Enable exclusive solo: either directly in the monitor section (if you use one) or in preferences (Edit > Preferences > Monitoring > Solo > [] Exclusive Solo)