Authentic genius is never recognized until the genius is dead, so the saying goes, but Stephen Sondheim is proving it a lie. At forty-three he has composed the music and/or lyrics for only (!) eight Broadway shows and one television special, yet practically everybody who knows or cares anything about the subject regards him as already the most important force in American theater music since Cole Porter. His songs are witty, sardonic, intelligent, brilliantly structured, and, above all, courageous. If there's a tired old rule to be broken, he breaks it. If there's a bright new idea kicking around, he has it. And since the whole rollicking history of Broadway musicals is seemingly at his talented fingertips, when a new chord must be struck, he strikes it. All of which explains why the opening of a new show by Stephen Sondheim automatically becomes an Event.

The event at...