Jonny Greenwood: So long to Jonny guitar

The axe hero Jonny Greenwood is the first Radiohead to go solo. And, he tells Andy Gill, there's barely a rock lick to be heard

Thom Yorke may be the driving force and most recognisable face of Radiohead, but for many fans it's the guitarist Jonny Greenwood, the thin, twitchy figure hiding behind a curtain of dark hair to Yorke's left on stage, who brings a crucial spice to the band's performances. That's Greenwood on their breakthrough hit "Creep", ushering in the chorus with those jarring, splenetic razor-slashes of distorted guitar that kick the song up several gears, sparking its smouldering self-disgust into something closer to cathartic rage - the kind of transformative moment that has become his signature contribution to the Radiohead style.

With his first solo album, Bodysong, however, Greenwood sets down a marker for a musical landscape entirely his own, abandoning the anchorages of rock'n'roll to push out into a wild, mysterious terrain where jazz, electronica, contemporary classical and avant-garde music combine and collide. It was written as the soundtrack to the director Simon Pummell's film of the same name, which draws on library footage from the past century to provide - to quote the press release - "a panoramic view of the experience of being human, from birth to death".

Pummell, who had previously made several short films, originally approached Radiohead a year and a half ago to provide music for the project, but, having just battled their way through the lengthy, arduous sessions that spawned the Kid A and Amnesiac albums, the band-members all opted to take a six-month break instead. All except Greenwood. "Six days is usually enough for me," he admits. "I'm addicted, I suppose, to working and being in the studio and writing music. But then, what's more fun that, really?"

Relaxing over tea in an Oxford hotel a day or two after returning from the group's latest American tour, Greenwood looks younger than his 31 years, retaining a freshness and sincerity that belies his position as bona fide guitar hero with arguably the biggest band in the world. There's no trace of the arrogance or side common among jaded, road-weary rockers who have spent much of the past decade traipsing from show to show, sucking up the acclaim of starry-eyed fans. He's polite and attentive, appreciative of any interest in his work, and eager to inform.

"My take on the film is that Simon has basically gone and visited lots of film libraries around the world and dug out material that relates to various themes he's chosen to do with human experience, for want of a less pompous phrase," he explains. "The result is that he's got footage from the turn of the century of people dancing, next to anthropological films of dancing around the world; and he's got scientific film from the 1960s of eggs and embryos, in a kind of collage thing. The way he described it to me at our first meeting was that originally, the whole point of filming a moving image was to record what's going on around you, and this is the kind of film that should be made more often, which I found interesting. Plus the idea of all this film just mouldering away, finally being seen. There's going to be a website where, once you've seen the film, you can research the clips and find out the history behind them. For instance, there's one really strange clip from Thirties Germany of two toddlers dressed as Nazis, carrying Nazi flags and playing drums, and you can read about how they grew up, and what happened to them."

Having pitched a few ideas to the director, Greenwood set about creating pieces to fit various sequences with Graeme Stewart, the engineer on the Kid A and Amnesiac sessions. "It was done in the same studio, with all the same instruments lying around, and some of the techniques we learnt for those albums are reproduced here, I'm sure," he says. "There was a lot of music to provide: the film doesn't have any dialogue in it, just music and images for an hour and 20 minutes. It was great not to have to leave room for dialogue, and not to have the musicians playing to click-tracks, just so they could fit in exactly with a car chase or what-ever, which I guess is true of traditional film music. Instead, I could just do three or four minutes of music in whatever mood, and people could play in free time - and occasionally, Simon Pummell would even edit the film to the length of the music, which was a real luxury.

"The trouble with that freedom was that I couldn't really repeat themes, as you can in a traditional film - because obviously, the music for someone giving birth wouldn't sound great being reprised for a shooting or a fight later on. So there's no repetition in it."

Their working relationship was much freer than in most movie projects, which usually involve the composer working to millisecond tolerances to fit music to a finished scene. Instead, Pummell would send Greenwood half an hour of footage that was about to be edited down to 10 minutes, so that he could get an idea of the intended mood; Greenwood would send back 15 minutes of music, and the two elements would expand or contract as required until they fitted.

The open-ended brief allowed Greenwood freedom to explore some unusual, even arcane, techniques and instruments. There's less guitar on Bodysong than might be expected; instead, there are tracks that blend pump organ, double bass and laptop electronics, or electronics, string quartet and glass harmonica (a spinning-wine-glass contraption), and even one on which he plays banjo, an instrument that Radiohead's producer, Nigel Godrich, would never let him play on the band's albums. "It was fun," says Greenwood. "It can be a very sinister instrument."

Several tracks feature the ondes martenot, an early electronic instrument invented by Maurice Martenot in the 1920s, for which Darius Milhaud, Arthur Honegger and Olivier Messiaen all wrote pieces in the Thirties. Serious players are rare these days, and the few remaining instruments are mostly regarded as museum curios. Radiohead's may well be the only working model in Britain, and they're trying to ensure it gets heard.

"I love the ondes martenot," Greenwood enthuses. "It's the most expressive electronic instrument that's ever been invented, I think, just so natural to play - neutral in a way, but so magical." A curious instrument akin to a more sophisticated theremin, the ondes martenot has several unique features, including a speaker strung with resonating strings, and an ingenious pressure-sensitive button allowing infinite control of a note's attack. "The button is the clever part, because you can do it staccato or very gently," explains Greenwood. "It's a very lyrical instrument in the hands of someone who can play it well - it's like someone singing. The part of the Star Trek theme that sounds like a woman singing is actually a martenot. Its players like to look down on the theremin and regard it rather as a toy - there's snobbery even in that field, which I quite enjoy!"

Greenwood uses the martenot alongside more recent technology to achieve unique effects - playing a bell sound from a laptop through the resonating speaker, or, as on the album's closing track, "Tehellet", using it with a vocoder in order to sing along with a string quartet. "I really like mixing old technology and new," he explains. "The ondes martenot is Twenties technology, the vocoder is Sixties/Seventies technology, and the string quartet is an even older idea. Putting them all together is what I'm most excited about."

His approach to musical sources is matched by Greenwood's fascination with hands-on methods of composition and recording. While no stranger to modern computer-music methods, on several tracks here he's not afraid to roll up his sleeves and edit pieces with the old-world implements of tape, razor blade and sticky tape, in the manner of the early Forties and Fifties exponents of musique concrète (although he finds their work too deliberately brutal and ugly for his taste, admitting: "I'm more a fan of music that's just a bit more magical and mysterious, and a lot of that stuff doesn't have that quality, I think"). On another piece, several asynchronous percussion tracks drift slowly into time together, in the manner of an early Steve Reich composition.

"It was a nice technical headache to work out how to do it, to have everything in time at the end but out of time at the beginning of the track, and slowly drift in," he recalls. "It was all done with tape, running at different speeds and backwards and so on, and me sat like a five-year-old on the floor of the studio with one drum at a time, picking up percussion instruments."

The cut-up method proved useful in conveying his ideas to other musicians. To show Gerald Presencer's jazz quartet the kind of thing he was after, Greenwood sent them a letter mentioning a few pieces in a similar style - notably Dollar Brand's "African Space Programme" - along with a tape collage he had made. The band responded with the exhilarating "Splitter", while the tape collage was deemed sufficiently different to appear as the track "Trench".

"Jazz was the obvious thing to do, because the only way I could think of tying different pieces of music together was to have everybody playing in the same scale - which obviously lends itself to jazz, because you can restrict them to only a few notes, and write themes for them. It was insane how such simple ideas were turned into music by them! The same with the string quartet: it sounds really banal, but it was a revelation to hear my arrangements played by real musicians."

The string arrangements offered Greenwood a belated opportunity to put his classical training to good use. Back in 1991, he was three weeks into his university course, studying viola, when the band signed with EMI, and he had to choose between the two musical paths. "So I suppose there was another, slightly harder-working me, who was headed for the back of the viola section at some minor orchestra," he reflects, adding mordantly, "Viola, which is already the non-instrument of the group!"

He took the chance to redress the balance on behalf of his first instrument when he wrote the string-quartet arrangements for Bodysong. "I got really bitter and gave the viola all the interesting stuff in this," he confides with a chuckle, "because I remember scraping along with all the simpler parts!" Even softly spoken classical musicians, it seems, can harbour grudges for years.

'Bodysong' is out now on Parlophone