What distinguishes "Sweeney Todd" from simple Victorian dramaturgy is its deliberate theatricality, its desire not just to scare us, but to invest the horror with irony. Nineteenth-century realism assumed its audience was naive and innocent; post-Brechtian theater presumes its audience is theatrically knowing and socially guilty….

Sondheim's score reinforces this complex emotional (or antiemotional) structure. In some ways it is his most melodic, richest work—yet, even at its lushest moments, the context never lets the music seem merely "beautiful." The tenderest moment, musically, for example, is a love song the vengeful barber sings to his razor. Another lovely song, "Pretty Ladies," is one Todd sings to distract the "customer" whose throat he most wants to slit. As one would expect, the score is full of wit and sardonic humor—the first act closes brilliantly with a duet in which Todd and his neighbor discuss how the professions...