@Lowell Background rack is a very powerful feature in Cantabile.
To keep things simple, i control a few general things here. The bindings for changing Songs and Song States are stored here so they are always the same buttons. Also Tap-Tempo and Panic!
There is a very good post from @dave_dore on how to use the background rack for send effects. Background Rack
I have three reverbs (Plate for Brass, Mid Hall as a general Rvrb, large Hall for FX) and a delay in my background rack.
You could even have instruments loaded in the background rack. I have never done it that way, but it would have the advantage that the sounds are not cut off when changing sounds.
best regards
Steffen