I like to imagine myself ready to answer this question at any moment in my rehearsal.
Why are we doing this particular warmup?
Why are we singing this particular repertoire?
Why are we spending ten minutes on this particular 4-bar phrase?
Why are you taking time away from singing to talk about the overtone series?
Why does this ensemble exist?
Why, why, why?
There should be a reason for everything we do together in rehearsal. I love it when students ask why questions, because it means they are thinking one level higher about the function and meaning of rehearsal, and because their question helps me clarify my rehearsal process and intentions.