'It's not a stage thing - it's a movie'

Ithink Sweeney Todd has endured for 150 years because it's a gripping tale," says Stephen Sondheim, creator of the acclaimed musical, Sweeney Todd: The Demon Barber of Fleet Street , which has now been adapted into a movie by Tim Burton with Johnny Depp in the lead role. Talking in London last week, Sondheim says: "It's a tragedy in the classic tradition about someone who goes out for revenge and ends up destroying himself."

The character Sweeney Todd first appeared in a story, The String of Pearls: A Romance , published by Thomas Peckett Prest in 1846. According to legend, Todd would cut his customers' throats, then send their corpses down a chute into the cellar below, where they were chopped up and used as filling for meat pies by his accomplice, the widowed baker Mrs Lovett.

In 1847, Prest's story was adapted into a play, The Demon Barber of Fleet Street . But it was British playwright Christopher Bond's 1973 play Sweeney Todd that first introduced the revenge plot now considered integral to the legend. In Bond's tale, Sweeney loses his wife and daughter after being unjustly sent to prison. He plots retribution against those who wronged him but his murderous impulses soon extend to the whole of society. In 1979, using Bond's work as a template, Sondheim brought the story to a wider audience in the stage musical he wrote with Hugh Wheeler. Making its debut in March 1979, it was unlike anything seen on Broadway before - original, witty and dark, with otherworldly music.

John Logan, who has adapted the musical for the screen, says: "What sets Sweeney Todd apart from other musicals is the solid emotional core. It's a dark but passionate story about a man who's wronged, seeks revenge and, in the process, goes mad. It's also about a woman who's in love with him but can't make a connection with him. And it's about a young girl raised by a brutal stepfather trying to find happiness. All these emotional lines collide in the film and the fact that it's heightened by music and singing makes it all the more lushly romantic."

A film version of Sweeney Todd seemed logical to Sondheim since his musical was inspired by a score from the composer Bernard Herrmann, best known for Vertigo and Psycho . "I've been a movie fan since I was a kid," says Sondheim. "When I was 15, I saw Hangover Square with a Herrmann score. It's a flamboyant Edwardian melodrama about a composer who goes crazy - when he hears certain sounds, he goes out and murders beautiful girls. I remember loving that score and I thought it would be fun to scare audiences and see if I could do it with singing."

Although director Tim Burton is known for his dark macabre films, Sweeney Todd is his first musical. "Tim is a perfect fit," says Sondheim. "In many ways, it's his simplest, most direct film, and you can see that he's telling a story he likes." Burton didn't see the original Broadway production but saw a performance in London while he was a student. "I'm not a big musical fan, but I loved it," he recalls. From the beginning, Burton approached the text as an old horror movie that would juxtapose beautiful but eerie music with dark and haunting images. Asked about their collaboration, Burton pays tribute to Sondheim as "a formidable man, very intelligent and passionate, a genius at what he does. What I respect and feel grateful for is that Stephen can let the story go - he understood that it's not a stage thing, it's a movie."

Sweeney Todd is Burton's sixth film with Johnny Depp, after Edward Scissorhands , Ed Wood , Sleepy Hollow , Charlie and the Chocolate Factory and Corpse Bride . Burton explains: "Every time Johnny and I work together, we try to do something different, and singing for a whole movie is not something we're used to. Johnny and I always want to stretch ourselves, and this was perfect outlet for that."

In 2001, before Burton was even contracted to direct Sweeney Todd , he visited Depp at his house in the south of France and gave him a CD of the stage production. Depp recalls: "Tim said, 'I don't know if you've ever heard this. Give it a listen.' I gave it a listen and thought, 'Well, that's interesting.' Then, five or six years later, the big question: 'Do you think you can sing?' 'I don't know,' I told Tim, 'I'll see if I can.' "

In the 1980s, Depp had played guitar in a Florida band, The Kids, although he never actually sang an entire song. "I was the guy who would come in and sing the harmony, very quickly," he laughs. "It would be all of, like, three seconds and then I was out, and I could find my way back to the dark and continue playing guitar."

"I said to Tim, 'I'm going to go into the studio with a pal of mine and I'm going to try and sing the songs, and if I'm close, then we can talk about it, or I'll call you and say, you know what, I can't do it. It's just impossible.' "

It turned out to be possible but not easy. Sondheim writes such complicated music that it made the performers "feel like climbing Mount Everest without oxygen and without Sherpas," says Burton. But although Sondheim was concerned about the musical adaptation, he was just as focused on the performers, as he explains, "I prefer actors who sing over singers who act. That doesn't always do the music good, but it does keep the story going and that's what's is important."

In terms of the story, Depp found the key to Sweeney Todd was to think of him not as a killer but as a victim. He reflects: "Sweeney is obviously a dark figure, but quite sensitive. He has experienced something traumatic in his life, a grave injustice. I always saw him as a victim." Depp also saw Sweeney as "a little slow. Not dumb, just a half-step behind. The rug was pulled out from under his perfect life. The only reason he came back was to eliminate the people who had done him wrong."

Sweeney's favoured instruments are his shiny cutthroat razors, his tools of the trade as a barber. Mrs Lovett - who is played by Tim Burton's wife Helena Bonham Carter - held on to them while he was in prison. Once back in his hands, they become his lifeline and means of revenge. "I serenade them in a song called 'My Friends,' " Depp explains. "These blades are an extension of me, the only love in my life now that my family's gone."

"Johnny's performance is extraordinary," says Sondheim. "Sweeney's desire for revenge and the simmering anger and hurt he feels carry the story forward, and Johnny finds the most remarkable variety within that narrow set of emotions. The intensity is at a boil all the time and he never drops it."

'Sweeney Todd: The Demon Barber of Fleet Street' opened yesterday in the US and is released in the UK on January 25

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