Now, "Sessions" is in session, and if the "authence sometimes talks back to the actors," well, what provides better feedback than talk therapy in a musical about a therapist? "We had 100 therapists in the authence one performance."There's a wince in his voice: "Maybe in five years; not now," he says. "It's not funny yet."Funny thing about this composer of a ballet ("The Seduction of Bathsheba") and author of A Minister, a Priest and a Rabbi ... He gets the joke even as he makes them. Indeed, writing a musical about therapists is a good mind game. It's not like every medical group could get their own show. "No," muses [Tapper]. "I couldn't have written a musical about gynecologists."