From Schmigadoon!, at the Nederlander. Photo: Matthew Murphy In an unsteady season on Broadway, we’ve gotten a surefire frontrunner for the award for “most musical.” Not in terms of the scale of its sets—we’ll leave that to the giant staircase in The Queen of Versailles , or whatever is going on with the flying vampires of The Lost Boys —but in terms of the most tropes crammed into one two-act stretch. If you respond to musical theater like a professor with a grading rubric, I can’t imagine you’