Radiohead frontman Thom Yorke once called bass player Colin Greenwood the band's secret weapon, as in the one who will chat to anyone, any time.

"It's not very flattering, really," responds Greenwood on the phone this week from Boston, where Radiohead launched the first date of its North American tour in support of its outstanding sixth album, Hail to the Thief. The tour brings Radiohead to Thunderbird Stadium Saturday.

"What he's referring to is when Thom wants to get off and have an early night and doesn't want to talk with anyone, then he deploys me."

It doesn't take long to realize why. You get the feeling Greenwood, a bookish type with a degree in literature, a knack for dressing frumpy and a famously huge appetite, would prefer to chirp and blather on about anything other than the subject of Radiohead. He's like the amiable and gentile British pastor, oblivious to the hard realities of life, so self-effacing and coy it's almost irritating, and just a little bit cuckoo.

For example, he'll happily tell you, in his sing-songy private-school-boy accent: "I just got back from having seafood with my brother and we had lobster. It was lovely."

During another recent interview with The Vancouver Sun, he was prone to exclaiming, "Yaay, and weee" as an expression of positivity for no apparent reason.

It makes for a pleasant enough interview, similar to having tea with Granny, who's mixed her medications. And besides, you think to yourself, you could be talking to Yorke on one of his bad days, when he's feeling sulky and precious, and hot-ass ready to take issue with the most innocuous of questions.

Greenwood, on the other hand, simply raises your suspicion that his twittering is a ploy to fend off anything controversial, which is most probably the case, since his answers to serious questions often sound stiff and rehearsed. Radiohead has said it is making every effort to avoid Clear Channel owned venues this time around, to circumvent the monopoly claimed by the concert behemoth.

"What we're trying to do is strike a balance between providing music and entertainment between people who want to come and see it without excluding audiences or places and trying to work as independently as possible at the same time," he rattles off.

Okay, then. But his reticence is forgivable. The five Englishmen who comprise Radiohead - singer-guitarist Yorke, Greenwood, his guitarist brother Jonny, guitarist Ed O'Brien and drummer Phil Selway - keep close to their hometown of Oxford, gobbling up books, writing songs, raising their children, hanging out with their girlfriends and friends at the local pub and, other than the requisite interviews or the occasional protest against the government, generally try to avoid the spotlight. Their unease with the publicity machine is almost palpable, and interviews often come off as gruelling verbal tugs of war.

The band's nearly clinical reaction to its massive popularity following the release of '97's OK Computer is typical of its mainstream reluctance. Musically, they responded with a two-strike diss of all things commercial with the remarkable Kid A and then Amnesiac in 2001, obliterating any hopes of an OK Computer Part II. But the obliqueness of the albums, particularly Kid A, nearly alienated them from one too many fans, and like a one-time drunk who found God and got all preachy, they've righted themselves with Hail to the Thief - an exquisite blend of mood and melody that's got something for the whole family.

"I'm just grateful that anyone listens to it, let alone turns out to the show," says an appreciative Greenwood, who claims he learned to play by listening to New Order, Joy Division and Otis Redding. ("A very soulful mix.")

"It's been good with us, because on one side when we play songs live, they are taken somewhere more special than on the record," says Greenwood. "But that's good for our sanity because we kind of construct our music so that we can have it a bit open ended when we play live, so we don't get too bored."

To keep things exciting when they recorded Hail in L.A., the band members rented new Mini Coopers and bombed around town. Selway's had a Union Jack on the roof, while Greenwood's flaunted the American flag.

It's almost fun to throw a celebrity question at Radiohead simply because it is likely to get them worked up. Yorke goes almost convulsive at the suggestion that he could possibly belong to such a club, and Greenwood is simply aghast. "It would just be a disaster," he says. "We wouldn't know what to say when we did meet [a celebrity]. And we wouldn't have anything in common with them. So what would be the point of meeting them in the first place? The whole thing would just be too mortifying... Could you imagine?" he asks, as if we were discussing the dropping of another atomic bomb.

Speaking of bombs, despite its controversial content and title, Hail to the Thief never did blow up in anyone's face. No death threats materialized. The title, a reference to George Bush, only ever inspired an onslaught of media questions about Dixie Chicks-style backlash. And Greenwood is for once sober on the topic.

"The only sort of irritating thing I found personally was when you would talk to certain people in Europe who would see it as an opportunity to slag off America and it's like, too easy. It's more than that.

"I had a really good one in Italy with a television journalist who said, 'Haven't you had death threats? Aren't you worried about censorship in America?' I said to the guy, 'You come from a country where the president has passed laws exempting himself from any kind of prosecution on corruption charges, and you are slagging off America. Don't you think that's a bit hypocritical?' And he looked at me, and said, 'We can't use that.'"

One of the album's best songs is "A Wolf at the Door", written by Jonny Greenwood. It almost fell victim to the overwrought process.

"It's one of my favourites, too, and it nearly didn't get on the record," says Greenwood. "I don't know why. I can't remember. I think it would have been terrible, though. That's the thing, if you spend too long doing things, you don't have a clue do you?"

Greenwood wants to shake up the band's work ethic next time around. He wants to write and record a few songs, and if they are beautiful enough, play them live before returning to the studio to finish the album.

"Spruce it all up over time," he says. "Break down the recording process."

As for solo projects, the band is keen on seeing Yorke dive in, and feels it could even be a beneficial exercise for their frontman, but they are more reluctant to go forth themselves.

"It's funny you should say that, because we were talking about it over the seafood today in Boston at the aquarium and we decided we wouldn't straight away," says Greenwood, referring to the idea of doing a side project with Jonny. "But my brother's done a wonderful [soundtrack] project called Bodysong, and it's really good. So that's really exciting. and it's coming out in October on EMI.

"But that's about as far as it goes, because we are still really excited about Radiohead stuff, and we have lots of ideas for that."

On what label these ideas will end up is another matter. Radiohead is currently between labels, having fulfilled its six-album contract with Parlophone/EMI. For the last several months, it has appeared to be in negotiations, though Greenwood is unable to say.

"We'll see how well the record does," he says. "Oh it will be fine. Uh, is there anything new? No. It's all completely up in the air. It's a very frustrating answer, but it's the truth. I wish I could say we've got all these plans or we haven't. But it's still nothing. Still waiting desperately to see whether anyone wants to carry on working with us again. I hope so," he adds, sounding falsely desperate.

When asked if he ever goes back to their catalogue, he makes several grunting noises like he's trying to dislodge something from his trachea.

"It's tricky isn't it?" he says finally. "They can be so evocative, they can send you back to places you might not want to go too as well."

Yorke, for one, has said that listening to his old albums has made him feel ill. Greenwood laughs-gasps at this.

"He has a violent reaction to any idea of nostalgia as an anathema concept to creativity. That's what he's doing."

Unlikely rock stars, perhaps, but what's not to like about Radiohead? With Yorke's ethereal voice a force in itself (he not only sounds haunted, he looks haunted), they make beautiful music independent of the verse-chorus-verse cycle that still somehow manages to prove accessible to our conditioned ears. In a world of yes-men and fame-seekers, they're trouble-makers with conscience.

Greenwood's reference to playing the new material says it all:

"It's been a good balance between challenging and satisfying."

Radiohead performs at Thunderbird Stadium Saturday.