Martin Kettle meets Russian pianist Mikhail Pletnev

Like many Italian cities, Turin conceals its secrets behind a stony facade. Walk down the Via Po and, unless a door has been left open, there is little hint of what lies hidden in the courtyards beyond. Venture through a doorway, though, and you grasp why the city is one of the grandest in Europe.

This makes it a very appropriate place to meet Mikhail Pletnev. Like Turin, the Russian pianist and conductor presents a severe face to the world. At the keyboard or on the podium, Pletnev can seem austere. But when he makes music, a very different man emerges. He does not need to play for long before you learn why he is one of the special artists of the age.

If there is an echo there of Pletnev's compatriot Sergei Rachmaninov, that is appropriate, too. Few musicians have been more reserved on the concert platform than the lugubrious-looking Rachmaninov. Stravinsky called him the only pianist who never grimaced. Few musicians, though, have ever communicated more profoundly from the keyboard and through their music.

For Pletnev, Rachmaninov has been a lifelong preoccupation. The young Pletnev's first recording, back in 1987, was of the neglected first piano concerto. Twelve years later, Pletnev made a treasurable recital disc at Rachmaninov's villa in Switzerland on the composer's own 1933 Steinway. His latest CD, issued this month, couples the third concertos of Prokofiev and Rachmaninov in performances conducted by Mstislav Rostropovich. And this month, Pletnev will perform the cycle of the composer's concertos for the first time in his career, with the Philharmonia Orchestra in London's Royal Festival Hall.

Pletnev has come to Italy to prepare for these British concerts. Extraordinarily for a pianist with so many Rachmaninov connections, he had never played the fourth and final concerto - the only one that Rachmaninov wrote in exile - in public until last week. "I wanted to have a warm-up before going to London. I wanted to listen to myself without having too much press attention," he says.

It is not merely the way Pletnev plays Rachmaninov that holds the attention. It is also the way he talks about him. "Rachmaninov was not a pianist," Pletnev says. "He was not a conductor. He also was not even a composer. He was a spirit. That's the definition of Rachmaninov."

Striking stuff. And it gets more emphatic still, as Pletnev settles into his stride. "Artur Rubinstein was once asked who was the best pianist he had ever heard. He named some pianists, very good pianists. And the interviewer asked him, 'But you heard Rachmaninov. What about Rachmaninov?' And Rubinstein replied, 'You asked me about pianists. But Rachmaninov was...' And he just raised his hands."

With a shrug of the shoulders and a wave of his hands, Pletnev copies the gesture. It is as though mere words cannot convey what he thinks about Rachmaninov. And yet the flow of words keeps coming.

"Rachmaninov is beyond easy definition," he continues. "Think of it like this. Horowitz was a pianist. This tells you about Horowitz. But it is not enough to say Rachmaninov was a pianist. For me, he was music. From the point of view of musical talents, I think that what was given to Rachmaninov by God, I can only compare with Mozart."

A large claim - not one that many people would instinctively agree with. Yet Pletnev has a big case to make. To support it, he tells a wonderful anecdote of the kind that one normally only hears about Mozart.

"There is a story. Once, he went to see his teacher Sergei Taneyev, at his house. While Rachmaninov was there, Glazunov arrived. And Taneyev said to Rachmaninov, 'Why don't you just get yourself something to eat in the kitchen while I speak to Mr Glazunov?' So Rachmaninov did so.

"Glazunov had come with a new symphony, and he wanted to show it to Taneyev. He sat at the piano and he played his new symphony, the first movement, and you know the style of Glazunov, it's not easy.

"And at some point Taneyev said to Glazunov, 'I have here another friend of mine, Mr Rachmaninov.' Rachmaninov came in and was introduced. And Rachmaninov said, 'I have also written a quite nice symphony. Would you like to listen to it?' So Rachmaninov sat at the piano and played the first movement of the Glazunov symphony, which he had just heard from the kitchen."

Pletnev has quite a reputation of his own for being able to memorise a score. But he claims that this aspect of his powers is waning. Learning the fourth concerto has been a struggle, he says. "What I used to do in 30 minutes, I now cannot do in six months. I'm too slow. My concentration is weaker. Before I was very fast in everything. But it is useless to complain."

It is hard to know how much of this to take at face value. Pletnev may talk eloquently about Rachmaninov, but he puts up shutters of irony when the subject turns to himself. He can no longer live in Russia, he says. But when I ask him where he now calls home, he replies poetically: "I live upon the Milky Way." The riddles continue. "I am finished. I am old," he says at one point (but he is only 46 and his diary is full of engagements for years to come). "I am not an artist," he says later (yet some think he is just about the most musical performer before the public at this time). "I have some abilities to play sometimes, and some people say it's not too bad," he allows.

And what to make of this statement? "I cannot tell the truth," he insists. "I never tell the truth. I will never tell the truth to my friends, and only sometimes to myself. I don't want to make people sad, because mostly the truth is sad. I think people should live in a positive way and should think positively. I don't want to spoil it."

But Rachmaninov also was a sad person, I venture. "Yes, extremely sad. Horowitz told me that Rachmaninov once said to him that he was always just about to burst out in tears."

In addition to writing his four concertos, Rachmaninov also made famous recordings of them during his years of exile in America. Though he is said to have remarked that Horowitz's recording of the third concerto surpassed his own, the composer's performances cast a long shadow over all later interpreters. I asked Pletnev how they affected his own readings.

"Look - every note played by Rachmaninov is great. He plays everything better than anyone else. And every note played by Rachmaninov sounds only like Rachmaninov. When I listen to Rachmaninov, it is of course fantastic what he does as a pianist. But when he plays, I hear the whole layer of Russian culture and history which he embodies, and which is gone - Chekhov, Tolstoy and Turgenev - a style of life and people and morality, everything together.

"But this has gone. It doesn't exist any more. When I was young and stupid I thought Rachmaninov's recordings were a challenge. But now I know better. It's useless to imitate Rachmaninov. I can imitate his playing, can imitate it quite well. But I cannot imitate what is behind his playing. An artist has to feel that he can do something differently. I accept things as they are."

· Mikhail Pletnev plays Rachmaninov's four piano concertos with the Philharmonia at the Festival Hall, London SE1, from November 16, then tours. Box office for all concerts: 0800 652 6717