Ed O'Brien cuts loose during his appearance at the all-star Neil Finn shows in New Zealand.

It was the kind of scene that would make recalcitrant Radiohead fans weep, those fans who yearn for the days when the band's songs had chord changes you could replicate on your $200 imitation Fender. It was also a scene that nearly made guitarist Ed O'Brien weep.

In an Edwardian theatre in central Auckland that had seen better days, O'Brien was standing on one side of the stage pulling out notes both dark and beautiful. Across the way was Johnny Marr, whose work with The Smiths 17 years earlier had inspired a teenage O'Brien to pick up a guitar. Even in the semi-darkness, you could see O'Brien's face switch from joy to disbelief to a state they refer to in the tabloids as "emotional".

Stop press: Radiohead member plays pop songs again. Stop press: they're not his songs. That expression - part cat that ate the cream, part boy in a lolly shop - is still there the next morning as a bbarefooted O'Brien, his hair still shower wet, curls his long legs up under himself. Later in the day, he will search local record stores for a copy of The Smiths's Hatful Of Hollow album to have it autographed by Marr.

Talking about the early rehearsals for the Neil Finn and Friends shows, he recalls a conversation about what to do if there are three and sometimes four guitarists on stage. "[We said] let's embrace the fact we've got all these guitarists and make them sound big, have them doing their thing."

You just know it's a line that would not have been uttered anywhere near Radiohead as they recorded the songs that ended up on Kid A last year and its sister album, Amnesiac, out on Monday. But did you know that, while all members of Radiohead agreed that the stadium rock band they had become had to end, immediately, they were not agreed on which direction to take? Ed O'Brien had visions of Marr and The Smiths.

"My reaction to OK Computer was 'let's come out with three-minute pop songs', three-minute songs, in your face, not sprawling out, no Paranoid Android," O'Brien says in his deep, perfect vowels. "There were several of us who talked about that, but it didn't happen."

What happened instead was the sound of one band stretching the boundaries of conventional rock. What happened instead was an album that mixed the cold steel of '90s electronica with the exploratory fragmentation of '70s German progressive rock in a way that was thrilling to those prepared to take the trip and just plain alienating to those who didn't. Kid A scored reviews both scathing and laudatory, lost fans by the score and yet topped the US charts.

They had to do it, O'Brien says, partly because of the "art school ethos of not going over the same ground" and partly to preserve sanity. "I don't think any of us wanted to carry on like that. It would have killed us," he says with a shudder. It almost tore the band apart.

O'Brien told Mojo magazine: "I honestly didn't feel I had a role to play [with the Kid A songs of singer/ songwriter Thom Yorke]. It was really difficult because, as a musician, I express myself more emotionally than cerebrally."

How did it feel to be that close to the death of a band? "We've always been like that," O'Brien says. "There's always been an element of that: we have lurched from crisis to crisis. There was always something every year. Doing this can play tricks on the brain."

A trick of the brain on first hearing Amnesiac is to believe that you have the next step for Radiohead, with the detachment shed for the starkly beautiful first single Pyramid Song and guitars a-jangling in Knives Out.Amnesiac was written and recorded at the same time as Kid A and it is in many ways a completion of the picture. Electronic sounds dominate, dramatic melodic sweeps that once marked their style are still avoided and Yorke's voice is again at times unintelligible.

But O'Brien contends that there is a stretching of that picture to incorporate more familiar faces of Radiohead. "[There's] a bit more emotion. The emotion is the key. There are loads of melodies on Kid A, but emotion is the thing on [Amnesiac] that engages you," he says.

"I like the fact that it is really diverse, it reminds me of the way we put together The Bends [the 1995 second album]. On Kid A and OK Computer what you are trying to do is avoid the listener hitting the skip button. With this album you can do that, the order is really important, but I think the songs stand out [on their own]. And they're such good songs, as well. Every single song may not be to everyone's taste but there are going to be bits and pieces that everyone could like."

Maybe what the two albums seem to be saying is that Radiohead can be any kind of band they choose. "I love that," O'Brien says. "I love the fact we're laying all our cards on the table. We can be a guitar band, we can still do that. We had to do the Kid A stuff but one thing we all came back to is [the idea that] it's great playing guitars.

"You have to get away from guitars because you come back and you have this renewed vigour and delight in playing these songs. That's reflected in Knives Out and Dollars & Cents and I Might Be Wrong. You can still do it and do it really well and dip into other sonic areas too."

Stop press: maybe those Finn shows weren't atypical after all.