LONDON, England (CNN) -- Cross one macabre-obsessed director with the grisly legend of a homicidal barber, add a lick of singing, a smart, oddball cast and what do you get?
Johnny Depp plays Sweeney Todd the murderous barber
One of the most anticipated films of the year: "Sweeney Todd -- The Demon Barber of Fleet Street". It joins a handful of films in the improbably eccentric horror-musical genre, but it's fast becoming known as the "singalong slasher."
Directed by Tim Burton and starring Johnny Depp, Helena Bonham Carter and Sasha Baron Cohen, "Sweeney Todd" is based on the award-winning musical by composer Stephen Sondheim. It is the tale of a serial-killing 19th century English barber who -- fuelled by vengeance after a corrupt judge ruins his life -- realizes the deadly potential of his blade on a murderous rampage around the streets of London.
For a director whose love of the gruesome is written all over films like "Beetle Juice" and "Corpse Bride," the story of the slicing, dicing serial killer was perfect. "It's my territory," nods Burton who has been "marinating" the project since he first saw the stage show 20 years ago. "It's quite a daunting task you know because [Sondheim] is such a brilliant composer and it's ... my favorite musical," he told CNN.
The music may be Sondheim's but the look and feel of the film is pure Burton. He has created a gothic vision of 19th century London for his cadaverous cast to inhabit, complete with his own ironic twist of wit. Burton says he fell in love with the humour of the stage show, but for the screen his aim was to get inside the emotional state of the characters. He likens the expressiveness he was aiming for to that of silent era actors.
"This is Burton's giant salute to classic horror films," says the film's star and long-time Burton collaborator, Johnny Depp.
Depp was recently awarded a best actor Golden Globe for his efforts as Sweeney Todd -- the blade-happy anti-hero of Burton's murderous musical.
Despite having exactly zero experience as a singer, Depp sang all his own songs. It is a testament to Burton's relationship with Depp -- they first worked together 17 years ago and "Sweeney Todd" will be their sixth collaboration -- that Burton didn't feel the need for any backup plan.
"When he said he could do it that was enough," Burton says of Depp. "I know him well enough to know that he wouldn't say that [if he couldn't do it]."
"It was a month or two and he was working privately on it, going through the process, and then he sang something that went beyond expectations," the director added.
Burton and Depp have teamed up on films including "Edward Scissorhands," "Sleepy Hollow," "Ed Wood" and "Charlie and the Chocolate Factory" -- performances which have cemented Depp's reputation as the misfit A-lister.
The actor and director are firm friends off-set too, drawn together by a shared sense of the absurd and love of old horror movies. "He knows me pretty much better than anyone," Depp admits.
But his old friend's confidence didn't make the prospect of performing in a musical any easier for him. "The whole idea initially of just singing, just exposing yourself on that level is ... it's frightening," Depp told CNN. "But it's one of those things where you try and challenge yourself, hope that you overcome your fears ... and in the process don't let your friend and director down. And not embarrass your family too much," the actor continued.
And Burton's gamble paid off: "He really made it his own thing which is a very difficult musical thing to do," he said.
Helena Bonham Carter co-stars as Todd's feisty, amoral partner-in-crime, Mrs. Lovett. The role was originally played by Angela Lansbury in a 1979 Broadway production, which won eight Tony awards.
Bonham Carter is Burton's long-time partner with whom he has two children, but intimacy didn't give her any advantages when it came to casting: terrified of his own latent nepotism, he made her audition nine times. In the end, Sondheim relieved Burton of his dilemma by choosing her. Bonham Carter, for her part, is said to have called the production "one of the toughest, most grueling rights of passage we went through in our relationship."
Bonham Carter's preparations for the role involved not only learning to sing -- she was also a complete novice -- but brushing up on her culinary skills too. In the film, Mrs. Lovett uses her baking skills and Todd's surplus "meat" to create diabolically delicious meat pies -- all the while singing and bashing pastry in time to the music.
"That was hard work. You have to make a real pie a bit like Blue Peter or Martha Stewart but at the same time you know, sing. A really complicated song too," explains Bonham Carter.
"Because he's such a clever person, he'd written into the song the pie-making so when you pick up the rolling pin and when you bash the dough and all that, it all has to be on time to the beat, so I'd just practice and practice. I think I've done it I don't know how many times ... completely to death ... about 300 times," she continues.
Bonham Carter and Depp -- already friends before the film -- formed a bond on set, especially when a newly pregnant Bonham Carter became suddenly bird-brained and couldn't remember her lines. "I was pregnant halfway through and my brain went, it just vanished. I couldn't concentrate so a lot of the time [Depp] would be off camera pointing like he's a parent reminding me of what I'm supposed to do because otherwise there was this blank," she laughs.
Everyone's favourite rogue, Alan Rickman plays a perfectly pitched English villain as the corrupt Judge Turpin, target of Todd's revenge. Another British actor, Timothy Spall, famous for his downtrodden characters and open-mouthed hangdog expressions, does a natty turn as Judge Turpin's vile, calculating henchman, Beadle Bamford.
Rickman summons up an impressive baritone, despite being yet another member of the cast with no previous singing experience. But with a dauntingly impressive career -- on stage in the Royal Shakespeare Company and more recently as a chilling Severus Snape in the Harry Potter films -- behind him, Rickman felt ready to put his talents on the line.
"Well, at this point I think I'm looking for the next cliff face to either fall off or climb up, because that's what is exciting. So this was like, well, here's a big challenge," shrugs Rickman.
It's unclear if the Sweeney Todd of legend actually ever existed. Some claim he never did; others have documented a comprehensive history of the notorious "demon barber." What is clear is that telling the bloody tale of Sweeny Todd on film was long overdue -- and who better than Burton and his improbable chorus to do it. "He's outdone himself," says Depp, shaking his head, "which I didn't think was possible after some of his past movies." E-mail to a friend