I was struck by the craftsmanship that holds “Urinetown” together. When the score does not nod toward the Hollywood of the 1930s, it winks at the Berlin of the 1920s musicalized by Kurt Weill and Bertolt Brecht, or glances at the Paris of the 1830s as immortalized by “Les Misérables.” And of course the title brings to mind Steeltown, the setting of Marc Blitzstein’s agitprop play with music “The Cradle Will Rock,” from 1937. Like that city, “Urinetown isn’t so much a place as it is a metaphysical place,” as Little Sally puts it.