Bloody revenge, grotesque comedy and the verbal pyrotechnics and soaring melodies of Our Father Who Art Stephen Sondheim -- "Sweeney Todd" is a cornucopia of musical theater delights, just as long as you don't mind the macabre.

And the fine touring production playing at Heinz Hall through the weekend has an intimate intensity, revealing new facets, evidence that "Sweeney Todd" is a classic that keeps on giving.

Still, something's wrong up by the stage: Audience members are seated in the orchestra pit, and not just because the big Heinz Hall house band is away in Europe. Has the incredible shrinking orchestra hit touring shows this hard? Where are the pickets?

Not to worry: This is the "Sweeney Todd" directed and designed by John Doyle, in which the cast of 10 accompanies itself, playing 23 instruments in varying combinations while it also acts, sings, dresses each other, makes sound effects and moves scenery.

So are they trying to put the stage hands out of business, too? Where are those pickets?

No, all's well: The cast plays its instruments to Sondheimesque effect, mixing blood with beauty and comedy with melodrama. Their instruments have a further eerie way of italicizing the lyrics or action that you don't feel when they're out of sight in the pit.

The most obvious example is the young lovers, both playing as though their cellos were substitutes for the bodies they cannot touch. At another point, Anthony grabs his cello as if protecting his privates. Mrs. Lovett tootles comically on her tuba and pings punctiliously on her triangle; Judge Turpin blats pompously on his trumpet; the Beggar Woman yearns through her clarinet; and Tobias laments via violin.

The scenery moving makes sense, too. Doyle has set the show in a madhouse, as you realize when Tobias is freed from a straitjacket at the start and returned into bondage at the end. In presenting their grisly story, the inmates (think"Marat/Sade") make use of whatever is at hand. So they're often in movement, rearranging the small stage with its limited pieces of furniture, preparing the buckets of stage blood they pour (as the light turns red and a whistle screeches) whenever Sweeney's razors drink their full.

If you just saw Tim Burton's movie, you'll be pleased to (re)discover the music omitted there, starting with the plangent "Ballad of Sweeney Todd." Granted, with just 10 instruments to work with at any point, the orchestrations aren't lush, but spiky is a good sound for this material, and the voices here are better.

Our classical music critic says I can't call it a chamber opera, but he's away with that big band, so I will, anyway. It has operatic passion. And Sondheim shows in "Johanna" how sweet gorgeous music can be but, in context, how creepy, too.

I do wonder how clear the witty, raunchy and chilling lyrics are. I'm no test, because I know the show well, but for some the verbal intricacy and the size of Heinz Hall must muffle understanding. The audience also has to keep actively engaged, to realize, for example, that a small white coffin plays the role of a barber's chair. And the striking lighting, all murky atmosphere, also requires audience focus.

This brings me to the size of the hall, which is far too big for such a show. (The set uses only half the stage width.) But we're told that the economics of touring prohibit using the Byham -- remember "Proof," last year?

David Hess is a forceful Sweeney, if not as charismatic as Broadway's Michael Cerveris (leaving Johnny Depp out of the equation). The most magnetic performance is Judy Kaye's Mrs. Lovett, who makes nuance vivid. Watch her clean her gruesome utensils with domestic sangfroid.

Lauren Molina's Johanna and Benjamin Magnuson's Anthony are funnier than I recall the same actors were on Broadway -- he, so callow, she so flighty, both achingly innocent. Edmund Bagnell's Tobias gives innocence a demented edge. Benjamin Eakeley's surprisingly dapper, sleazy Beadle is able to turn the word "virginity" into a perversion, but Keith Butterbaugh's Judge Turpin lacks an extra degree of cold command.

Pittsburgher Diana DiMarzio's Beggar Woman seems primarily atmospheric, but if you know who she really is, you'll enjoy all the clues in the show's blocking. The friend I was with had never seen "Sweeney Todd" and had the pleasure of the awful revelation.

It's really closer to tragedy than melodrama -- less Greek than Jacobean, with just about everyone hoist on their own petards.

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