Trip-hop soundtrack for Vatican's Pope DVD

Captain Jack Sparrow should keep a weather eye out: a dead Pope is on his trail. Pirates of the Caribbean may be top of the DVD charts now, but tomorrow the Vatican releases a film of the late John Paul II's speeches set to music – by an agnostic British composer of horror movie scores.

Simon Boswell was given unprecedented freedom to edit the Pope's voice for Santo Subito! – which means "canonise him quickly", the phrase on banners held up at the Pope's funeral in 1995. The music ranges from Gregorian chant to trip-hop; the visuals resemble a pop video. "A lot of it is quite trippy," says Boswell. "Ecstasy in a drug sense rather than a religious sense. It's quite psychedelic."

The composer, from Tufnell Park, north London, started out with gory Italian movies two decades ago, but has now scored 100 films, including hits such as Shallow Grave. This time he worked for royalties only, but says: "If 5 per cent of all Catholics buy it, this will sell more copies than Michael Jackson's Thriller."

While not converted, he was impressed by the priests who commissioned him. "They're doing this for the love of the man, and I can understand that."