Robert Mammana and David St. Louis Photo by Tania Thompson/SCR

It's a big, long (2 hours 45 minutes), complicated, and difficult piece, currently staged by South Coast Repertory, an Orange County theatre company, on a smallish stage with room for a nine-piece orchestra tucked above stage right. Under the circumstances, they should be admired just for mounting the work, which, at the press opening performance, had come together but still needed more seasoning.

Subtitled "A Musical Thriller," Sweeney is set in a London filled with corruption: street vendors hocking "special tonics" that do nothing promised, law enforcement at all levels lording power over the helpless, a beggar woman offering prostitution as well, and "buyer beware" at every turn. To this London comes Benjamin Barker (David St. Louis), a barber who was falsely sent to prison by Judge Turpin (Robert Mammana) and in the process lost both his wife and daughter Johanna (Juliana Hansen). Taking the name of Sweeney Todd, Barker vows revenge against the judge and his "enforcer," Beadle Bamford (Nicholas Mongiardo-Cooper).

Barker comes upon Mrs. Lovett (Jamey Hood), who is barely getting by, making "the worst pies in London." She does, however, have an upper room where Sweeney Todd can open a tonsorial parlor (barbers did all kinds of things in this era). Todd and Lovett, by necessity, fight off various schemers and, by accident, Todd kills one of them. Thinking how to dispose of the body, Mrs. Lovett comes up with the idea of using the remains in her pies.

And we're off to the races, as the pies become a huge hit.

Mr. Sondheim's score sounds best with operatic voices, though very little of it is more than an operatic hybrid. The beggar woman's (Erica Hanrahan-Ball) vocal "alms" motif is an operatic fragment, and some of the opening numbers ("The Ballad of Sweeney Todd," which recurs throughout, "No Place Like London," "The Worst Pies in London") have operatic roots, but the ballads ("Johanna," "Pretty Women," "By the Sea," "Not While I'm Around") all resonate as belonging to musical theatre. Even the sophisticated patter song at the close of act one ("A Little Priest") would feel at home in either genre.

South Coast Repertory has cast musical theatre singers in the principal roles, and some of their voices are more "operatic" than others (only one, ensemble member Katy Tang, has any significant opera experience). Singing over large orchestras, opera performers are often helped along by projected text. No such help is provided here, and periodic diction and blend problems within voices and between voices and orchestra were the result at the performance I saw.

The advantage to hiring musical theatre performers is that they can usually act better than opera performers, but the acting here seems somewhat "by the numbers." There is one scene, in act two, between Mrs. Lovett and her helper Tobias (Conlan Ledwith), that crackles with energy and nuance in a way that should certainly be a model for the rest of the scenes.

Director Kent Nicholson moves along the production along well and is aided by solid contributions in scenic design (John Iacovelli), lighting design (Lap Chi Chu), sound design (Cricket Myers), music direction, (David O), and choreography (Kelly Todd). Melanie Watnick's costume design goes above and beyond "solid."

As Sweeney, Mr. St. Louis embodies "revenge," down to his basso resonance. As Mrs. Lovett, Ms. Hood still seems to be finding her way, except in that "model" scene with Mr. Ledwith. In secondary roles, Devin Archer and Ms. Hansen are nicely paired as the young lovers, Anthony and Johanna.

The "bones" are solid here, and I expect this respectable production to improve as the performances age.

Sweeney Todd: The Demon Barber of Fleet Street, through February 16, 2019, at South Coast Repertory, 655 Town Center Drive, Costa Mesa CA. Performances are Sundays, Tuesdays, Wednesdays, and Thursdays at 7:30 p.m., Fridays and Saturdays at 8 p.m., and matinees Saturdays and Sundays at 2:30 p.m. Pay parking is available in several nearby structures. Tickets may be purchased at the box office, online at www.scr.org, or by phone at 714-708-5555.

Other cast members include Roland Rusinek and Brent Schindele.