Alfred Brendel is not giving interviews. In fact, at the moment, he is not planning to speak to journalists ever again. One of his agents in London gives a rather good impression of his gentle, pained, central European accent: "No, no more journalists, pleez." Nevertheless, he is just embarking on his grand 70th birthday tour (which finishes in August) and, this winter, he publishes his third and most comprehensive book of musical writings; not to mention the latest batch of CDs he has released, which will add to his already mountainous discography. The problem, it seems, is that a couple of months ago, in advance of his 70th birthday, he had a number of journalists in to his north London home in Hampstead over the course of one day, and found the experience rather bruising and disappointing. Not unreasonably, perhaps, he has decided that his writings, his concerts and his recordings speak eloquently enough for themselves.
There is an inherent problem with writing about music: the languages only translate superficially. It is a problem that is all too obvious in any bookshop: the music section is squeezed between the fat displays of books on cookery and architecture. The titles are either forbiddingly dry or inconsequentially light. Since his first collection of essays was published in 1976, Brendel has been trying to fill not so much a niche as a chasm. But then, as he says of the difficulty of musical analysis: "I think one should sometimes try to do the impossible."
His latest book, Alfred Brendel on Music, gives us not just a view of his progression as an artist over the past 40-odd years, but of the development of music appreciation. Here are essays pleading for Liszt and Schubert to be taken seriously. "I know I am compromising myself by speaking up for Liszt," he wrote in 1961 (Liszt is currently viewed as a tiresome technique freak). In clipped sentences, he lays out the ground rules for performance. Speeds should be kept in check, excessive rubato avoided. And we, the listeners, are not spared. "It would be nice if the public were to shed a few prejudices," Brendel concludes, with barbed politeness.
The shy figure from the concert platform reveals some unsparingly mordant views. Of Beethoven's G major Sonata Op 31 No 1, he writes: "The pianist who has not succeeded in making somebody in his audience laugh at the end of this sonata should become an organist." But he is also capable of an understated, slightly crushed sense of humour. In his footnote on the playing of Schubert's four-hand works, he begins by warning that during one performance, he became entangled in Daniel Barenboim's evening suit because they had spent all the rehearsal time in shirtsleeves. Later, he recalls stopping during the first few hushed bars of Liszt's Sposalizio to tell the audience: "I can hear you, but you can't hear me."
The earlier writing is often much more serious and committed. Aged 36, he proclaims the pianist's manifesto: "It is our moral duty to make music in as visionary, moving, mysterious, thoughtful, amusing, graceful a manner as we are able to." It is a forbidding list of demands. But Brendel suggests that the demands never end. Time and again, he refers to the "problem" of Beethoven; he has updated a chapter mournfully entitled "Coping With Pianos"; he even refers to Mozart's Sonata in C major, superficially his simplest, as "treacherous".
It is presumably this side to Brendel that barred him from featuring on the Radio 3 programme Private Passions, on the grounds that he is "too serious". But classical music - perhaps more than any other art form - needs its intellectuals. The celebrated Beethoven interpreter Stephen Kovacevich gave a masterclass at the Queen Elizabeth Hall in London a few weeks ago. He was lucid and engaging. His students were, at times, banal. A shocking key change would lose all element of surprise by a whacking ritardando. Kovacevich asked one of the pianists how she would describe the barmy, jittery first movement of Op 31 No 3. The answer was "happy".
As Brendel concedes, this is where you bump up against the limits of exegesis. It is all very well being aware of an important harmonic progression, he says, but if you don't feel it, then knowledge is useless. He quotes Schoenberg's dictum that formal analysis is often overrated because it shows how something is done, not what is done.
And that is why Brendel sets such store by live performance. There can, in the end, be no greater insight into a piece. He points out that when Beethoven marks a crescendo on a single note, in a concert hall, you can only convey that through gesture. Extraordinarily, he even says that when he first saw himself on TV, he noticed all sorts of tics and grimaces that contradicted what he wanted to do musically. So he had a big standing mirror made and put it by the side of the piano, so that he could begin to co-ordinate his movements with what he wanted to express.
Glenn Gould famously denounced concert halls as places where people went in order to catch musicians playing wrong notes: the equivalent, presumably, of watching Formula One in the hope of witnessing a fatal crash, or watching skiing to see a nasty fall. Brendel flatly disagrees. He, in fact, argues that where the voices, the dynamics, the character, rhythm and timbre of a piece are well handled, a few missed notes can almost add to the excitement. The studio, in contrast, can be sterile. "Those who consider spotless perfection and undisturbed technical neatness the prerequisites of a moving musical experience no longer know how to listen to music."
Brendel is right. His favourite recording of Beethoven's Hammerklavier Sonata is a live performance from 1983. Mine is a hissy tape, made by my parents on their hi-fi in 1975, of a Radio 3 live relay from the Royal Festival Hall. Sviatoslav Richter was on a rare trip from the Soviet Union. His playing alternates between a chilling, quiet bleakness and great forearm smashes of chords, some of which bear only a passing resemblance to the correct notes. It is mesmerising. At the end, the audience moans. And carries on moaning until he plays an encore - characteristically, no less than the whole bloody fugue all over again. He is met by a wall of sound. The Radio 3 announcer tremulously wishes him "Godspeed" back to beyond the Iron Curtain. After that, studio recordings of the Hammerklavier are just too polite.
Brendel's live recordings of the Mozart sonatas, released recently, are just as instructive. These are pieces that have been dragged through some truly lousy performances, such as Glenn Gould's perfunctory, disdainful, overly fast efforts. Beyond sharing a predilection for sotto voce groaning, Brendel's performances have nothing in common with Gould's. Brendel is the master of thoughtfulness. He tells you exactly where he is going and what he is attempting to convey. It is admirable, even if you disagree with the approach. In the B flat K570 sonata, I don't like the change in tempi in the first movement; and the last movement is too portly to be lilting or witty. But his rendition of K331 - the only one of Mozart's sonatas that consists of a theme and variations - is a revelation. His dynamics are bold but tender. He manages to turn the final variation (the Alla Turca) from a charmless romp into a dance showing Turkey as viewed in 18th-century Vienna. His triumph, however, is the haunting Rondo in A minor K511. It is not simperingly beautiful in his hands, but precise and clean. For him, the musical line does not just mean giving a phrase its correct shape, but carrying a line of thought from the beginning to the end of a piece.
It seems right that Brendel should be turning to the Mozart sonatas. Age, he readily admits, constrains technique. Five years ago, he said that he wished he had had a go at the Bach Goldberg Variations, but it was too late now. In fact, it seems almost shocking to think that he should have won his Gramophone awards back in the Seventies for his Liszt recordings. But the Mozart sonatas are no light touch. He quotes Schnabel's aphorism, that Mozart's sonatas are "too simple for children, too difficult for artists". Not so for Alfred Brendel. We are hearing an artist reaching not the end of his career, but the summit.
Alfred Brendel on Music is published by Robson Books (£16.99). Brendel's latest releases of sonatas by Mozart and Schubert are available on Philips. His European tour includes five dates in London between May and June
Tim Franks is a political correspondent for the BBC