You don't expect improvisation from a classical pianist. But the audience calls the tune for Gabriela Montero, she tells Arminta Wallace

Look at the cover of the new album by the young Venezuelan pianist Gabriela Montero and you see a typical young classical musician - trendy haircut, thoughtful pose, leather sofa. Listen to the music on Bach and Beyond, however, and you hear something else entirely. For a split second, you'd be forgiven for thinking that someone had shoved a Keith Jarrett or Brad Mehldau CD into the wrong box. Yet Montero has a musical voice that is all her own. Furthermore, she insists that she isn't a jazz pianist and that what she's doing when she improvises on themes by Bach or Rachmaninov or Chopin is totally consistent with the traditions of classical music.

It's when she does this in live performance, however, that the fun really starts. "The way I improvise is just to sit down and play whatever comes out," she says. "But when I started doing it in concerts, people often didn't believe that it was an improvisation. They had a lot of trouble understanding that the music was really being created right then and there. So a friend of mine suggested that I ask the public for a theme - number one, so that they would believe that it was really improvisation, and two, so that they could follow the process and that I could involve them in the whole thing."

This, then, is what she will probably do when she plays at the National Concert Hall in Dublin. Get your suggestions ready, folks. What sort of themes have audiences suggested to Montero in the past? "Oh, my God - anything," she says. "Anything from Mahler, Tchaikovsky and Scarlatti to the Beatles. To 1980s music. Or a cellphone ringtone. As long as people can carry a tune, it's no problem. They can give me anything they want."

IT WAS AT the suggestion of the people at her record label, EMI, that Montero recorded a series of improvisations on Bach themes at the Number 1 studio in London's Abbey Road last year. And it was, to that label's credit, a terrific idea. The disc is that rare event in classical music nowadays, something which is both familiar, yet new and fresh - without being forced or gimmicky. "The idea," Montero explains, "was to take a great master's melodies and then recreate them and transform them into something else.

"I was reading a review of the CD," she adds, "which was a fantastic review, you know? Yet another time somebody says, yes, this is great, this is beautiful, blah, blah, blah - but did she really improvise it? So I'm going, 'Oh my God, how frustrating'. I went to the studio; I asked my producer, OK which themes are we using; we chose some themes and I sat down and I just started to play. And that was it."

These days, when Montero plays live, people want her to play tracks from the album - difficult to do, when you've made them up on the spot in the first place? "It has been a very contradictory thing for me," she admits. "And so I've finally had to learn some of my improvisations by ear." By listening to her own recording? "Absolutely. We actually had somebody try and transcribe a couple of the improvisations, you know? Put them down on paper. But I discarded that, and I said 'OK, I have to do this myself'. I learn by ear in any case - it's a big part of how I approach music - so I had the capacity to do it. But I have to say that I found it very strange to learn my own improvisations. Very, very strange."

Montero first came in contact with a piano at the age of eight months. "I received a two-octave little toy piano for my first Christmas, and I started to pick out the tunes that my mom sang to me to put me to sleep at night," she says. She was playing melodies with two hands by the time she was a year and a half old, and improvising by the time she was three.

"My first teacher in Caracas, who was a wonderful teacher, would say to me; 'What would you like to improvise for me today?' I was four years old and it was completely natural for me to improvise."

As she grew up and pursued a classical training, however, she wasn't always encouraged. "I had one teacher who, for years, said; 'Don't do this any more - it's ridiculous, it's not worth anything.'"

For a long time, therefore, she kept this part of her musical talent to herself. Then Martha Argerich, the Argentinian pianist with whom Montero was studying, overheard her improvising and was ecstatic. "It was Martha who persuaded me that it was possible to combine my career as a serious 'classical' pianist with the side of me that is rather unusual."

TO SAY MONTERO is unusual is putting it mildly. Improvisation is seen as a jazz thing nowadays and isn't encouraged in classical circles, except under certain highly limited circumstances; it is, for example, okay for church organists to improvise during some religious ceremonies. On the concert platform, however, the written page rules with a rod of iron.

"Nobody is doing it - which is strange," says Montero, "because we know that the great composers all improvised. And of course improvisation and composition are very intimately linked. Improvisation is like an instant composition. I think the inspiration all comes from the same source; the only difference is that when you compose, you take more time and a lot of thought goes into it. Whereas improvisation is like an outpouring of music that is just there."

What comes out, though, surely must go in at some point? Or does Montero produce, in her improvisations, rhythms and harmonies she has never - consciously - heard?

"We're definitely all shaped by what we hear and what touches us," she says. "And in every age, the new musical expressions are - in a way - inspired by the old influences. Beethoven was inspired by Haydn, for example. So there are always these connections."

But she herself, she says, listens to very little music. "Anyone who has lived with me can tell you that - because I have a radio in my head the whole time, 24 hours a day. I hear this music all the time. I hear a sound, and after a few minutes I realise that I'm improvising on that sound. There's a lot of information inside me from all the repertoire that I've played. But within all of that, there's my own language. It's not that I want to sound like this composer or that one. When I improvise, it's not something that I control - it comes from a different place. The less I think, the more free and complex my improvisations are. Thoughts can imprison us, to a big degree."

Montero still plays the classical repertoire but only, she says, the pieces she really wants to play. But though she enjoys going to stage to perform with one of the big orchestras - on the occasion of our interview, she is due to play with the London Philharmonia at the Queen Elizabeth Hall - she says there's no comparison between a concert whose programme is pre-planned and the freedom of improvisation. "The world that you inhabit in the classical world is different," she says. "The feeling of going on a stage and not knowing anything of what's going to happen is just wonderful. I think most people would be terrified - but for me it's absolute freedom, and I love it. Of course it's a real journey for me every time I play one of the great concertos. But, yeah, that thing of going on stage to improvise - it's a free-fall. Like flying. I love it."

So, by all accounts, do her audiences. Not surprising, perhaps, for she's taking them right inside the creative process, giving them a glimpse of the magic of genuine music-making.

"You build a very close relationship with the public," she says. "It's great to see how people get so excited. They speak out, you know? There isn't that distance between the artist and the public that you would find normally in a theatre. Some of them even come up to the stage and play a melody on the piano. Or everyone starts to sing. It's wonderful; it really is."

Gabriela Montero will perform at the National Concert Hall next Thursday as part of Note Productions' Contemporary Concert Series