Preview: Ennio Morricone, Hammersmith Apollo, London

During the filming of Sergio Leone's gangster epic, Once Upon a Time in America, Robert De Niro and his fellow actors performed their scenes to the movie's score. "At first, De Niro complained, because he thought it was inappropriate to act with the music disturbing the take," says the composer Ennio Morricone. "But Leone insisted and so De Niro accepted. And, in the end, he said it really worked well, because the music was also good for the rhythm, the timing and the stress of the interpretation."

For Morricone, who has more than 450 film scores to his name, including The Good the Bad and the Ugly, The Mission and Cinema Paradiso, the trick has always been to work in different ways. "Some directors have shown me the edited film, others have given me the screenplay, others have shown me some footage," he says.

"Some directors, like Leone, for whom I composed the main themes before starting to film, told me the plot and explained to me some shots that he thought of filming."

Morricone's first film composition was for Luciano Salce's Il Federale in 1961, and 45 years later he is still hard at work, composing the score for Giuseppe Tornatore's new film, La Sconosciuta. Writing usually takes Morricone two or three weeks. "I've realised that having a lot of time for a film doesn't always help," he says. "Sometimes it is counterproductive, because film music needs immediacy. It must not distract the audience with too complex ideas. It must be spontaneous."

"A film composer must know and understand the way the great classic composers worked," says Morricone. "He needs to learn and acquire a sense of the form and control of music, learn and acquire a strong curiosity towards any musical experience."

Morricone will perform some of his many scores as part of this year's Don't Look Back series, for which he is accompanied by Hungary's Gyor Philharmonic Orchestra and the Crouch End Festival Chorus Choir.

19 and 20 July (08706 063 400; www.seetickets.com)