The musical and dramatic achievements of Stephen Sondheim's black and bloody "Sweeney Todd" are so numerous and so clamorous that they trample and jam each other in that invisible but finite doorway that connects a stage and its audience; doing themselves some harm in the process.

That is a serious reservation, and I will get back to it. But it is necessary to give the dimensions of the event. There is more of artistic energy, creative personality and plain excitement in "Sweeney Todd" … than in a dozen average musicals.

It is in many ways closer to opera than to most musicals; and in particular, and sometimes too much for its own good, to the Brecht-Weill "Threepenny Opera." Mr. Sondheim has composed an endlessly inventive, highly expressive score that works indivisibly from his brilliant and abrasive lyrics.

It is a powerful, coruscating instrument, this muscular partnership of words and...