The first time you hear Kid A, the fourth Radiohead album, you'll probably scratch your head and think, huh? What are they on about? For starters, why are the guitars only on three songs? What's with all the muted electronic hums, pulses and tones? And why is Thom Yorke's voice completely indistinguishable for most of the time?

Be assured, you're not alone. Mojo described a first impression of it as "just awful", while Music Week said it was "plain frustrating". And, more surprisingly, your reaction mirrors that of Kid A's producer Nigel Godrich, who also engineered and produced Radiohead's past two albums, The Bends and OK Computer.

"I think he thought I'd lost my marbles," grins Thom Yorke. We're discussing the album in a cafe in Cowley Road, in his home town, Oxford. "He didn't understand why, if we had such a strength in one thing, we would want to do something else. But at the same time he trusted me to have an idea of what I wanted, even though he didn't understand what it was for ages."

A lot of people think Radiohead might have lost their marbles, or that they have become so precious and removed from reality that they've counted themselves right out of the game. There will be no singles released from Kid A - and there aren't really any there, not even of the seven-minute scale of Paranoid Android. (Although Optimistic, the rock-est moment of the album, with its driving bass and almost militaristic drumming, will be released to US radio as a promo-only lead track.) Nor will there be any videos. There will, instead, be "i-blips", short video images designed for the net with soundbites from album tracks, downloadable from fan sites and the record company site. Oh, and they're touring the UK and Europe in a customised 10,000-capacity tent - a space free of corporate logos.

The wisdom of these unconventional methods is, of course, debatable. The industry is watching it all with great interest: some are secretly waiting for it all to backfire so they can gloat at Radiohead's folly; optimists who operate at the fringes of the music business are hoping that these methods may engender a new spirit of adventure in the marketing-driven superficiality that has marked the charts for a number of years. Fans don't really care. They've already been scouring Napster for recordings of gigs performed earlier this year, they've been logging on to radiohead.com and reading guitarist Ed O'Brien's recording diary for the past 12 months, and they will be happily trotting along to the tent shows and queuing up for the new album when it is released.

All of this is far removed from Radiohead themselves, for whom these measures were a necessity, not something they perversely dreamed up. Simply, everything that happened after the release of OK Computer - partly documented in the tour video Meeting People Is Easy - has given the band, and Yorke in particular, a pathological fear of falling into the same patterns again.

It wasn't so much the acclaim that was the problem. In 1998, Q readers voted OK Computer the greatest album in the world. A new UK albums poll by Colin Larkin, canvassing 200,000 punters, has The Bends at number two, after the Beatles' Revolver, with OK Computer at number four. But Yorke says of such polls, "Well it means nothing. That sort of thing never really did my head in, because there was no way of relating to it."

For Yorke, who turns 32 in October, the unpalatable paradox was that everything good they had done had been stripped of personal meaning and reduced to hyperbolic headlines. The band felt manipulated, like record company puppets, or media dancing bears. The reward for doing great work, it appeared, is being made to feel completely trite. This is fine for Oasis, for whom the music took a back seat to marketing long ago, but for Yorke and Radiohead, it rendered their entire purpose futile.

Yorke's reputation has been inflated to that of mythical miserabilist of a generation, wracked by neuroses and self-doubt. Today he seems engaged, calm and conversational, not difficult or obscure at all. So I ask Yorke the most banal of questions: Were you really that unhappy? And he stares at me as if I've just asked him if he thought Hitler was such a bad guy after all.

"I was a complete fucking mess," he spits. It feels like an accusation. "When OK Computer finished, yeah. I mean, really, really ill." Do you know why? "Just going a certain way for a long, long, long, long time, and not being able to stop or look back or consider where I was, at all. For, like, 10 years. And not being able to connect with anything. Basically becoming unhinged, in the best sense of the word. Completely unhinged."

But you don't seem like that now. "No." He half-smiles. "It took a while."

Where was everyone else in the band? Did they have that? "Oh yeah, possibly not as bad as me, but in different ways. We'd lived a certain way for so long that we weren't really functioning properly.

"There's nothing more boring than a rock'n'roll star," he continues, "someone who has been on the road for 10 years, expecting attention wherever he goes, drinking himself stupid, who is obnoxious, incoherent, uncreative and has a massive ego. There's nothing more pointless.

"And I think by this time I am supposed to have fucked myself up permanently, or be dead," he adds wryly. "I'm supposed to be so fucked up now that I can't work anymore. But I'm not. And that meant that I had to take a bit of responsibility for what I'm doing. But I'm not 'being responsible' - you can't be responsible in an 'adult' way about it, either."

The perceived burden of artistic responsibility can lead to inane political posturing and self-indulgent output, and although Yorke knows he will probably be accused of both, his convictions and pursuits could be attributed to anyone with even a mild awareness of the exploitation of third world resources, who has felt a modicum of middle-class white guilt and wanted to try to do something about it in a sensible manner. For Yorke, this includes attending the May Day protest.

"I'm a champagne socialist, apparently," he grimaces. "Someone called me that last night, I got into a massive row with him. The protests themselves are pretty nasty affairs. I went on the one in London, and there were so-called undercover guys walking around in bullet-proof jackets with long lens cameras and two armed bodyguards, walking through the crowd taking photos of 'troublemakers', that basically meant everybody in Trafalgar Square. Personally, I was really happy to get involved in Jubilee 2000 because it is a mainstream, acceptable face of resistance against the antics of the IMF and the World Bank. But equally, I am interested in the unacceptable face of it, in terms of the media coverage, the disruptive elements, the anarchists, because I don't really care what methods are used to make the IMF and World Bank so incredibly unpopular that they dismantle it. I don't really care how it happens, as long as it happens. That's the point."

In terms of Radiohead's place in the global market as a consumer product, Yorke is not naive or hopelessly idealistic. He's just trying to create a situation where the band feel more in control. Hence no videos, which he describes as "cheap TV ads". The "i-blips" are intended as straight-up Radiohead adverts, the rationale being that TV ads "are more like the videos, so we might as well go straight to the source. You're lying if you're pretending that it's not a product, that you're not trying to sell something."

Although there have been prognostications to the effect that Kid A is meant as an arty pisstake designed to fob off the lumpen masses, Yorke says it's nothing of the sort. "I wouldn't be involved in it if I wasn't aware that it was going to be a product. I always wanted whatever I did to end up in the high street, no matter what it was, because to me, there isn't anywhere else to go. It is art, but then, it's not. It's music! And I'd be wary of thinking, oh, it's challenging, because that's not it either. Challenging is like that free jazz, that fucking terrible free jazz that came after Coltrane: it's all complete whack."

So, Radiohead had no grand plans going in to record the follow up to OK Computer. For the first time, they also had no record company deadline, which proved as debilitating as it did liberating. Yorke only had fragments of songs, like How to Disappear Completely, which debuted on tour in 1998. Before moving into their own studio space in September 1999, Radiohead had three attempts at recording and songwriting in Paris, Copenhagen and an old mansion in Gloucestershire. Yorke intended these sessions to remove the band from working on "songs" as such, for them to work more like programmers and end up with a set of sounds and textures. And much has been made of Kid A's electronic sound, and Yorke's embracing of the Warp back catalogue - Autechre, Aphex Twin. But it would be simplistic to think that Yorke churlishly decided to abandon the guitar sound of The Bends and set the band off on a new course.

"I worry that people will think that, within my neurosis about what we've done in the past, I have just gone off and said, 'We must be electronic, all this is shit.' That wasn't the point. You can't just sit in a room together and play in one way for the rest of your lives and expect it to be wonderful. It's not going to happen," he says, wearily and a little sadly. "Even though that's what you think you should be doing, even though that's what you've always done, you hear a sound and you don't respond to it. When you get to that point, it feels like the ground is being pulled from beneath you. You're falling through space and it's a fucking nightmare. Every day you think, well, maybe we should stop. Maybe there's no point to this, because all the sounds you made, that made you happy, have been sucked of everything they meant. It's a total headfuck. And you've got no one to blame.

"If you spend your life being a creative person and expend energy on regretting stuff you've done before, you are fucked, because it will cramp you and you'll never be able to work again. I think I skirted around the edges of that for a while."

So, Kid A. What is it really like? After a few listens, the same emotional feeling contained in previous Radiohead music begins to glow through - it's just contained in an unfamiliar form. To punters familiar with the more leftfield genres of electronic music, it won't be much of a shock, and to everyone else, well, there are at least another couple of dozen songs recorded, some of them in a more graspable guitar vein that are being played live. Yorke smiles and shakes his head when probed about them, quipping "They're in a vault!" Speculation is rife that they'll appear as early as next spring. Or not. For the moment, Yorke is happy just to be happy.

"Once we finished this record, I started being a little bit easier on myself," he says. "Because I understood a little bit better where I was supposed to be. All the way through making Kid A, I was thinking, maybe it'll never happen. And the fact is, it did happen, we produced something I was happy with, I managed to get sounds that I wanted out of my head and on to tape as much as we could. It meant that I could be a little bit happier about the place I was at."