After the storm

He is a perfectionist French violinist, she is a fiery Portuguese pianist, and together - when not fighting - they are a dream chamber duo. Michael Church meets Augustin Dumay and Maria João Pires

Whatever it is that makes a good chamber duo, Augustin Dumay and Maria João Pires are often thought to exemplify it, and when they take the stage at the Barbican on Thursday, they'll evoke the usual sentimental response. The tall, willowy Frenchman and the diminutive Portuguese firebrand were indeed once an item, off-stage as well as on, but that didn't last, for reasons they are happy to explain. Like Astaire and Rogers in "Let's call the whole thing off", they were driven apart by everything, from what to eat (Pires is a proselytising vegetarian), to what to drive (Dumay likes smart new cars, she loathes them), to how to work – Dumay likes to have a concept in his mind when he approaches a new piece, while Pires prefers to jump straight in without preparation. Both admit to a combustible temper, which can lead to lively scenes behind closed doors.

Pires: "Sometimes, we can go for days without a fight, and then suddenly – pouf! – it comes. Like all human beings, we fight over stupid things – one bar, or even one note. When we were working on Beethoven's sixth sonata, we fought over a bar. I said I wanted energy in it, he said, 'But it's written piano'. I replied that I didn't care, so then he asked the sound engineer, at which point I got completely mad, and said I absolutely didn't care what the sound engineer thought – I just knew that the bar had to have energy. Then we started screaming at each other, and I said right, get another pianist, I'm off!" According to Dumay, the spat was all a matter of nerves, fatigue and tension. "That day it got to her, the next day it could have been me who walked out. Anyway, she came back in after an hour, and the bar was OK."

Their more substantive disagreements are over tempi, which Dumay regards as normal: "We all have different heart rhythms, we all have a notion of time that suits us, which is unique to us. It's the time each person takes to say things." Pires: "I get sick of the way everything these days is reduced to tempo, as though that was the only problem to solve." Dumay: "It's become the lowest common denominator in music. It's the tree that hides the forest." Pires: "A conductor will often ask me: 'What's your tempo? This one? OK – let's go!' But real music doesn't work like that. Merely finishing together is a pathetic goal."

Temperament aside, there's one very good reason why this brilliant duo are pulled in different directions, because Pires's major energies – and all her concert earnings – are devoted to the school she's set up at her farm in a remote and poverty-stricken part of central Portugal. Some of her pupils are local children, others are young pianists who come for intensive tutorials, which are largely devoted to lifting what she calls "the curse of fame".

"I think that it's normal and healthy to want to be respected," she explains. "But that need is quite small, and respect from family and friends should be quite enough. Nobody actually needs the whole world to acclaim them. Pianists who are obsessed with fame get destroyed by it. If by chance your work makes you famous, you should regard it as an accident, of no significance. Now, to tell a child all its life that it's going to be a genius – to train it to need adulation – is to give it a sick- ness: it's serious child-abuse. My classes are not designed to help sick people get more sick."

The idea of her school goes back to her childhood. "To when I was playing with the piano, rather than really playing it. Many years later I decided I wanted to see if my experience could be shared by other children. I still feel very close to the person I was aged three – much closer than I do to myself aged 30. Even now, if I see a room with nothing in it, I get excited about what I can do with it, how I can transform it. I've always felt sorry for people who grow up without the space to create."

Her kind of music teaching is the antithesis to that which lays down exactly what repertoire a child must play. "To avoid the attitude that, when you've done this and that, then you are a pianist. Where is your self in all that? And look what happens when a supposedly gifted young musician says she wants to stop playing the piano. They tell her she's crazy!"

At all events, this Barbican concert will mark the launch of the Deutsche Grammophon set of Beethoven sonata recordings that she and Dumay have laboured for five years to complete. I happened to be present when they were recording the first, and got a whiff of the stresses involved. Outside, a blizzard was blowing, while inside the studio, tempers were commensurately frayed. Constantly changing humidity had played havoc with the instruments, said Dumay, but that was nothing compared to the "changing weather" inside their heads. I was struck by the way their playing lost none of its freshness, as take followed take.

What also surprised me was Pires's willingness to let Dumay do the edits. "That suits me fine," she explained. "Because I couldn't do it. I trust his judgment – even if I think he does sometimes look for too much perfection. I never like to go back, to revisit old recordings, and that goes for my solo recordings as well. When I play, I play: that's all. All I care about is the piano, and how it feels under my fingers. Plus the acoustics, insofar as they affect the way I hear it."

So, how do they see these sonatas' trajectory? For Dumay, each represents a different world: "The first has traces of Mozart, the last has a purified quality." Pires elaborates: "The first five deal with the external world, and the rest deal increasingly with the inner world. Number 10 moves into a freer state, a spiritual realm beyond the body. Now that we've recorded them all, that is the one I most like to play. Number nine – the Kreutzer – feels like Beethoven's last struggle with the world, and it makes me physically tired to play it."

Augustin Dumay and Maria João Pires will play Beethoven Sonatas Nos 1, 9 & 10 for piano and violin on Thursday at the Barbican, London EC2 (020-7638 8891)