Oh, those crafty studio marketers. Look how they advertise Tim Burton's “Sweeney Todd: The Demon Barber of Fleet Street” - as a stylish, macabre thriller about a mythical hair-and-beard man (Johnny Depp) who wages a bloody campaign of murder and vengeance behind the quaint facade of his London barbershop.

And so it is. But what certain TV ads fail to mention is that Burton's movie is also a musical, adapted from the Stephen Sondheim-composed Broadway blockbuster, itself based on playwright Christopher Bond's definitive 1973 tragedy, in turn inspired by stories first published in the pulpy “penny dreadfuls” of Victorian-era British literature. One can only imagine how non-musical-loving audiences - expecting a big-budget slasher flick - will feel about the bait-and-switch.

Then again, maybe not. Because if any musical has the potential to “turn” your average lyric-phobic, musical-hating horror fan, this is the one. Haunting, hilarious and utterly, wonderfully ghoulish, “Sweeney Todd” isn't just the most entertaining big-screen musical since “Chicago,” it could be Burton's long-awaited masterpiece.

Depp plays Todd, né Benjamin Barker, a one-time star of the London grooming scene who returns from a 15-year overseas exile for crimes he didn't commit. Needless to say, he comes back to London a much darker man, both in mood and appearance, with an angry streak of white in his inky hair and the kind of ghastly, moribund mien that Burton often favors in his heroes (or antiheroes, as the case may be), from “Edward Scissorhands” to the Burton-produced “The Nightmare Before Christmas.”

Returning to his still-vacant shop in the fashion district, Barker meets Mrs. Lovett (Helena Bonham Carter), a baker of meat pies - the “worst pies in London,” she sadly warbles - who fills him in on the sad fate of his wife and child. Enraged, Barker retrieves his beloved silver straight-edge razors (his “friends,” he calls them) and swears revenge on the man responsible: Judge Turpin (Alan Rickman), a corrupt, loveless figure whose infatuation with Barker's wife started the whole sordid affair. Worse still, Turpin adopted Barker's now-grown daughter (Jayne Wisener, as the proverbial caged songbird) and is raising her as his own.

Though Depp's vocal range falls somewhere between “limited” and “Milli Vanilli,” he is magnificent as the anguished Barker. Adopting the alias Sweeney Todd, promising to “drip rubies” from his razors, the barber navigates a riotous fiord of scammers and villains, including the Italian tonic-peddler Signor Adolfo Pirelli (“Borat” mastermind Sacha Baron Cohen, hilarious as an oily charlatan) and the ratlike Beadle Bamford (Timothy Spall from “Enchanted,” always the henchman). Even the innocent are cruelly shoved into his meat-grinder machinations, including a smitten young sailor (Jamie Campbell Bower) who hopes to free the daughter from her gilded prison.

There's a darkly fearsome philosophy at play in “Sweeney Todd,” mirrored in both Rickman's hanging judge and Depp's ruined family man, so disgusted by human vice that he turns his murderous rage into industry, concocting a trap door behind his barber's chair so he can simply dump his victims down to Mrs. Lovett's pie ovens below. Throat-slittings, cockroaches, cannibalism and rape - no wonder Barker views the world as “a great black pit … filled with people full of”… well, you get the picture.

Against this dreary backdrop, even the modest flashes of human decency seem disproportionately bright. Depp is the star, but Bonham Carter is the movie's soul as Mrs. Lovett, who - as Todd's devoted co-conspirator - dreams of marital bliss amid the stacks of meat and buckets of blood. How gorgeously deluded. This, friends, is why women are the fairer sex.

‘Sweeney Todd: The Demon Barber of Fleet Street'

Stars: Johnny Depp, Helena Bonham Carter, Alan Rickman, Sacha Baron Cohen

Behind the scenes: Directed by Tim Burton, from a script by John Logan

Rating: R for graphic bloody violence

Running time: 1 hour, 52 minutes

Grade: A