Sight Readings: Bach by the numbers

REVERED BY Mozart, Beethoven, and Chopin; hailed by Schoenberg as the first 12-tone composer; embroidered by jazzmen, and played on every instrument under the sun - surely Bach needs no defence today? Oh yes he does, replies Rosalyn Tureck: he's trivialised and traduced as never before. To reinforce the point, she presses into my hand An Introduction to the Performance of Bach (book one of three), then follows it with a daunting clutch of essays by mathematicians, biologists and musicologists (Journal of the Tureck Bach Research Foundation) which include a rumination of her own entitled "Musical Authenticity: Is It a Legitimate Offspring of Janus?" Your starter for 10.

There are people who regard this doughty octogenarian as a pedant, but nobody writes her off as a crank. Two reasons to take her seriously have just hit the record shops: a CD of Bach's monumental Goldberg Variations (Deutsche Grammophon), and a CD of his Partitas (Philips Great Pianists of the 20th Century). For this Chicago-born Russian of Turkish extraction is not only a great pianist, but an astonishingly consistent one: while the variations were recorded last year, the Partitas were laid down in the Fifties, and both are characterised by the same marmoreal clarity. You'd almost say they emerged from the same session.

In one of her essays, she likens a musical score to a flower, with analysis being the process of its systematic dismemberment, "in order to learn what makes up the full-blown flower as an entity". She quotes with approval Debussy's definition of music as "the arithmetic of sounds". This, she says, is the stark, demystified reality of creative art. For 70 years she has been fixated on Bach, who belonged to a society promoting music as "sounding mathematics".

The trigger for this fixation was a sudden, blinding insight. "A week before my 17th birthday I was playing a particularly dense and complicated fugue, and I went into a trance. How long it lasted, I don't know, but when I came to, I knew I'd seen both the multi-levelled structure of the concept, and the technique required to fulfil it. Like Alice, I'd gone through a small door into an infinite green universe, and I wanted to stay in that universe for ever." She has done just that.

The new technique was both simple and exceptionally difficult, demanding that the player abandon the notion of right hand/ left hand opposition - melody versus harmony - on which classical music is largely based. Bach was thus put in line with Boulez and the serialists, and an entire performing tradition was overturned. "At first, I was as clumsy as a baby," says Tureck. "It took me three days to do four lines. But as my fingers absorbed my vision, it gradually got faster. Each finger had to be absolutely independent, to bring out all the parts evenly, without a trace of muddiness." Bach, she believes, should not be thought of in linear terms: the connections are vertical and diagonal, not merely horizontal. "There's a density in him, where everything is simultaneous." If you listen at random to either of the new recordings, you will instantly get the point.

You'll also notice another striking difference from other recordings of this music: very little pedal, and 57 varieties of staccato. For, as Tureck herself observes: "There's only one kind of legato: if the notes are connected, they're connected. But if they're staccato - if the notes are detached - the possible nuances are endless. Sometimes my fingers are playing with four different detached touches at once."

Which brings us to her most celebrated imitator, the egregious Glenn Gould. Tureck's records, wrote Gould, reflected "playing of such uprightness, to put it in the moral sphere. There was such a sense of repose that had nothing to do with languor, but rather with moral rectitude in the liturgical sense." When I ask whether she will now return the compliment, she hesitates - "That's a pointed question!" - and then delivers a put-down so graceless that I'm glad Gould didn't live to hear it. "He picked up the principle, but he didn't understand it. I don't just do it for variety, to keep the ear enthralled" - this said with lip-curling contempt. "He was talented and clever, but his idiosyncrasies were the result of a desperate desire to be noticed. I can't approve." Then she adds a coup de grace. "Idiosyncratic playing has nothing to do with art."

It's always a mistake to ask one sacred monster to appreciate the eccentric virtues of another; Gould's glorious intensity inhabits a different planet. So what other pianists does she like? A pause, a sigh: hers is, I realise, a very big ego. Should all aspiring pianists read her treatises, and apply them to every piece of Bach? "Of course. If they're serious." But it's fantastically laborious! "So? Who said art was anything else? Everyone today says enjoy. Enjoy means don't work, don't feel too deeply, don't think too hard, don't take any responsibility. Is that how you're going to spend your life?" I retreat to the back of the class.

But I sense, all the same, that she's a good teacher, and not just because of her declared reluctance to develop an army of little Turecks. It may sound finicky to devote three decades to the study of ornamentation per se, but her records reveal the structural strengths that lie in Bach's trills and appoggiaturas, when these are properly handled. For example, the Goldberg Variations, she says, are "a monument to one of the greatest minds that ever lived, with all its passion and beauty and humour".

Her Oxford home is stuffed with tapestries, paintings, and exotic instruments, but great minds are her preferred milieu. She was a teenage groupie of electronic-music pioneer Leon Theremin; Bertrand Russell, Isaiah Berlin, and atom-bomb inventor Robert Oppenheimer were among her friends; the scientists who share her symposia are leaders in their fields. "All good scientists are artists, and vice versa," she says as a parting shot. "They breathe the same oxygen."

MICHEL PETRUCCIANI lives! Yes, he may have died last week, aged 36, but this week sees the release of his latest CD, which reinforces his already solid status as a jazz immortal. Petrucciani Solo Live (FDM 36597- 8) bears the fruits of a wild session in Frankfurt, and has all the hallmarks - large structures, high fancy, sinewy strength - with which his fans will be familiar; one marvels yet again that so diminutive a pianist should be able to create so big a sound. For Petrucciani, who suffered (atrociously and heroically) from glass bone disease and had to use special stirrups to operate the pedals, was just 3ft tall, and too disabled to walk.

Everything about him was extraordinary, and so was my encounter with him at a London hotel. For 20 minutes he held forth on his friends, heroes and family, propping himself up between a low table and a chair. Then a fire alarm went off, followed by an order to evacuate. "OK, let's get the fuck out of here!" he shouted. We were on the 11th floor, and were told that lifts were out of bounds and that we'd have to walk. He refused all offers of help, choosing to lower himself painfully step by step all the way to the ground. Then, in great good humour, he carried on where he'd left off.