William Finn introduced the first of his irresistible autobiographical--or at least semi-autobiographical--musicals 37 years ago with In Trousers, during which married Marvin, who must be a version of the bookwriter-songwriter, ruminates about his sexuality. Still obsessed with the subject--as anyone driven to get to the bottom of his soul would be--Finn reworked Marvin, his wife Trina, son Jason and lover Whizzer Brown into March of the Falsettos.