He once likened his singing voice to the mating call of a rutting stag.

But Johnny Depp did not let it get in the way of arguably his most challenging film role yet -- an all-singing turn as the serial-killing barber Sweeney Todd in a remake of the Stephen Sondheim musical.

Directed by long-time collaborator Tim Burton, Depp is pale-faced and dark-eyed in the grim story of revenge, blending into the black-and-white world of grimy 19th Century London punctuated only by the vivid red of his victims' blood.

His sinister sidekick is Mrs. Lovett, played by Burton's partner Helena Bonham Carter, whose meat pies start to sell like hot cakes when she teams up with neighbor Todd in an ingenious venture to dispose of the countless bodies he produces.

I never sang before in my life, so I had to kind of find my way to it, Depp told journalists in London at a recent press launch for the film, which premieres on Monday. I didn't know if I would be able to hit a note, to be honest.

To find out, Depp called a member of the band he played for in the 1980s and recorded My Friends, an early song in the musical. When producer Richard Zanuck heard the recording, he believed Depp could pull it off.

The 44-year-old star of the hit Pirates of the Caribbean films, as well as Burton pictures including Charlie and the Chocolate Factory and Edward Scissorhands, said he hoped to bring something new to the Sweeney Todd legend.

I just thought it might be a great opportunity to try to find a new Sweeney, a different Sweeney, in a good way a slightly more contemporary, almost like a punk rock Sweeney.

Asked why he took more risks in his career than many actors, he replied: I think it's probably something in between hard-headed and ignorant.

SONDHEIM BLESSING

It was script writer John Logan's job to condense the three-hour stage musical Sweeney Todd: The Demon Barber of Fleet Street to a two-hour movie. Sondheim had approval rights over the parts of Todd and Lovett and the choice of director.

Some songs were shortened, others cut altogether, and the focus of Burton's lens is as much on the acting as the singing.

Depp and Bonham Carter are joined by Alan Rickman as the malevolent Judge Turpin, who wrongly imprisons Benjamin Barker to steal his wife, and later his daughter.

Sacha Baron Cohen of Borat fame plays Pirelli, a buffoonish rival barber who threatens to reveal Barker's true identity after he takes on the guise of Todd.

It is generally accepted that Sweeney Todd never existed, although some have argued that the personality is based on fact.

One legend has it that he was born in London in 1748 and arrested aged 14 for theft. After becoming apprentice to a prison barber, he opened a shop on Fleet Street, where he carried out his grisly crimes with the help of Mrs. Lovett.

Burton recognized it was not obvious material for a Christmas release, which tend to be feel good and child friendly.

Pulling few punches in a film full of gore and blood, the movie has been given an R rating, meaning anyone under 17 must by accompanied by a parent or adult guardian.

I've seen productions where they've tried to be a bit more politically correct, and 'Let's lessen the blood', and it really deflated the impact of what the story is, Burton said.

The film is scheduled for limited U.S. release on December 21.