Bertolucci's model composer

Composer, actor, model, rebel. Ryuichi Sakamoto just likes to follow his instinct.

Nagisa Oshima's chilling essay on prison-camp sadism, Merry Christmas, Mr Lawrence, left the image of two faces imprinted on the mind. David Bowie, buried to the neck in sand as he stoically awaited death; and, looming over him, a figure whose sculpted visage expressed the fastidious, passionate disdain of the samurai code. Much of the drama was played out in silence, but from time to time, to underscore tension or signal a gathering storm, music would be heard: a sweetly insidious presence on the fringe of consciousness. Its composer - and performer - was that disdainful samurai: Ryuichi Sakamoto had previously neither acted in a film, nor had he composed for one, yet in effect he took over the show.

That was in 1983, when his main claim to fame was as the champion of Japanese techno-pop. Since then he has composed for the Olympics, built a music- publishing empire, carved a niche as the world's most eccentric singer- songwriter, and acquired a long shelf of Grammies and Globes for his scores for Bernardo Bertolucci. This Friday he will take over the South Bank with a film retrospective and a public interview, and also a concert, which will be broadcast on the Internet, at the Festival Hall. Here, supported by a violinist and a cellist, he will perform music from his new album.

Most of this music is reworked from his film scores, but if you talk of him as a film composer - as I did at the beginning of our interview - you meet a polite but firm rebuff. "I am a musician. Sometimes, my role is to compose for films." The long tumbling locks are fashionably bleached, and the sculpted features are heavier than they were a decade ago, but the halting manner is instantly recognisable.

How does he view his performance in that film? "I don't like it at all. My consciousness does not allow me to see myself on screen with pleasure. The way some people don't like the sound of their recorded voices." A curious formality of diction, punctuated by careful pauses. "I think my acting skill was a little better in The Last Emperor, where not many people recognised me. I had a moustache, and was one-armed. I played a film magnate, but in reality I was the chief Japanese spy." But this man also models clothes, for Gap among others. Does his camera-shyness extend to this as well? "Modelling is much easier than acting. I do it when people ask me." He says this in a half-whisper, with the ghost of a smile.

One of the tracks on the new CD is called "Rain". Is this anything to do with Madonna's video of the same title, in which he co-starred? "No. That video was not a good experience. She was OK with me, but very nasty to everyone else on set." The "Rain" we shall hear on Friday is the development of a short track from The Last Emperor: a simple theme with a Nymanish ostinato, which in its new version has become cleaner, more muscular, and more fanciful.

He's on record as saying that making music on stage is not a creative act. Does he still believe this? "Yes. When I play on stage, I am just repeating what I have created. If I were really to show my creative process, it would take a week, or a month. But not even jazz improvisation is creative: it's based on preparation beforehand, on worked-out lines of musical thought."

It's hard to pin down precisely what makes his screen music so recognisable, but each score manages to fuse ethnic sounds - North African chants, Indian percussion, Chinese woodwind - with melodies which have a strong emotional sweep: he always makes it seem simple. But when he describes his working methods with Bertolucci, this seems to be the result of much calculation.

"First Bertolucci asks for a big general theme, so I give him a choice of three or four. He can never imagine how it will sound when I play it on the piano, so I have to record demo tracks with the real instruments. When he has chosen, I start variations, and smaller themes. But I have to be very specific about length: I calculate the differences between film rates and musical tempo, and my music is created to fit the visual structure exactly. But Bertolucci changes that every day, which drives me mad." Very politely mad, one suspects: it's hard to imagine this gracefully inscrutable creature ever losing his cool.

Yet he describes himself as a lifelong rebel, and in the Japanese context this is true. Born in 1952 to an editor father and hat-designer mother, he was blooded in the student radicalism of the late Sixties. His first musical hero was Bach, then came Beethoven (he taught himself to play the Third Piano Concerto), then Debussy (whose string quartet he laboriously transposed for the piano). Then came the Beatles, then Satie, then John Coltrane. And then he hooked into the Darmstadt group - Boulez, Stockhausen, Cage, Messiaen. "All these people, from Bach onwards, were breaking the rules, and constructing their own. That is what I try to do."

The most decisive piece of rebellion came when he rejected everything the Darmstadt group stood for. "I realised that their audience was too small. I needed real contact with normal people." Hence, as a response to the German techno-pop group Kraftwerk, the formation of the Yellow Magic Orchestra. "The idea was - yellow, in between black and white. A magic of our own to counter that of Europe and America. A Japanese, an Asian magic."

The Yellow Magic Orchestra disbanded, reformed, then disbanded again; his scores gradually became repositories for musical shards from every phase of his past. In among the slow-rap songs of his 1984 album Sweet Revenge - decorated with pictures of Sakamoto swooning on beds of coloured fur - one track could have been written by Erik Satie. More remarkably, one of the tracks on the Sheltering Sky album is pure Sixties atonalism. Did Bertolucci need much persuading to accept this? "No. It was fun to do. And very easy."

Where is he steering to now? Is there a grand plan in all this? "No. I just follow my instinct." So his instinct has told him to embark on this current world tour? "No. That was my manager!"

As he is dragged away for a photo-shoot in Hyde Park, I ask what music he is currently listening to, and he lights up in a way he has not done so far. "Brazilian - from Bahia! It is the most mixed music of all. African, European, Latin American - it combines everything!" Then he makes an extraordinary gesture, as though opening his heart. "This music is growing inside me!"

n On Friday 'Wuthering Heights', 1.20pm, 'Merry Christmas, Mr Lawrence', 3.30pm, Sakamoto interview, 6pm, are all at the NFT, London SE1 (0171- 928 3232); the concert, also on Fri, at 7.30pm, Royal Festival Hall, London SE1 (0171-960 4242). The album '1996: Ryuichi Sakamoto' is out on the Milan label