Outside the theatre, beneath the bookshelves of the Institution's considerable library, tables and notice-boards are covered in press cuttings, programmes and record sleeves. The subject of this exhibition is the star of the lecture-concert, Dr Rosalyn Tureck. Some of the record sleeves bear a Jacob Epstein bust of Tureck, rough-hewn, uncompromising, but coldly beautiful. Others display the comparative warmth of recent photographs; but the music is virtually always by Bach - Preludes and Fugues, the Goldberg Variations, Partitas. For most British music-lovers there is no other Rosalyn Tureck than the Bach player, scholar and editor (of An Introduction to the Performance of Bach, to name just the most popular of her many publications). And that image is largely self-imposed.
Chicago-born and now in her late 70s, Tureck was a child prodigy who dared to defy fashion and tradition. Her teachers included the much-revered Olga Samaroff, who, when confronted with the 17-year-old's resolve to play Bach in an entirely new way, deemed her pupil's innovations impossible. But Tureck had recently emerged from an intense revelation about a specific Fugue, and would not retreat.
'I felt I had gone through a small door into an infinite green universe,' she tells me, 'and this image has stayed with me all my life. I was not going back through that door just because my teacher said that it was 'impossible'. I went ahead, had to chop down every blade of grass by myself, and it is on that foundation that my work has developed.'
The 'work' she speaks of is a journey through Bach's infinitely complex polyphonies, a profound preoccupation that manifests itself not only in her studies but, pre-eminently, in her playing, which boasts some of the most beautifully controlled counterpoint to be heard anywhere, either on disc or in concert.
But the 'High Priestess of Bach' has also visited other musical climes. She started out with the same Rachmaninov, Tchaikovsky and Chopin that any respectable young lady pianist of the time might tackle - 'but I couldn't leave Bach,' she says. 'After the first two years of playing all these varied programmes, I gave a series of six all-Bach recitals, one every week, and they went well. I was immediately engaged for the Institute of Technology in California, where they have all those great scientific minds, while at the same time I was touring in concertos and giving world premieres' - including music by David Diamond, William Schuman and the British premiere of Aaron Copland's granitic Sonata. Recent appearances, however - such as that captured on her new CD (VAIA 1024-2) taped live at a concert in South America - have seen her return to selected Brahms and Schubert.
Tureck's love of science and 'the new' extends to electronic music, which has fascinated her since childhood. At 10, she was taken to hear a concert that Lev Theremin gave at Great Orchestra Hall in Chicago and went back stage to meet him.
'I was so interested, that I sneaked on stage to see the instruments. And I still remember those huge black coils and towering speakers; I had to look way up at them - they were on very tall poles.' Six years later, in her first week at Juilliard, Tureck saw a notice on the bulletin board announcing that Theremin was in New York offering a scholarship. 'And I went right down there, tried out, won it and studied with him; that was at the age of 16 or 17. In the spring I made my Carnegie Hall debut - playing Theremin electronic instruments.' Later on, Robert Moog gave her one of his synthesisers, which she soon incorporated into her lectures - 'Bach's F minor Sinfonia, on piano, harpsichord, clavichord - then the Moog]'
The idea of playing early music on different instruments from varying periods poses Tureck no conceptual problems - provided the performer is fully educated in both the history of style and what Tureck terms 'the psychology of listening - of interpreting sounds and lines, locating melody, finding out where a harmony is going, and why, what it came from and how we view it today. A habitual way of listening, interpreting, formulating - what's happening in the music.' She has spent years investigating embellishments in Bach's work, their effect and their meaning in the context of his oeuvre as a whole, from a simple bourree to the St Matthew Passion.
But the path of scholarship is notoriously uncommercial, and concert managers were persistent in trying to re-direct Tureck towards more profitable ventures.
'In those very early years,' she recalls, 'other young pianists used to say to me: 'My manager says I have to play this kind of programme, otherwise I'll never get engagements.' And I used to say, 'What would the managers do without us?' I was engaged in a town called Chicoutimi, which is north of Quebec - you go to the end of the world, drop off, and still have another eight hours before you get there] So I sent my programme to my manager, as usual. He called me up, exasperated. 'You can't play such a programme in Chicoutimi,' he said; 'you have no Chopin on it. Even Serkin plays Chopin there]' But I convinced him that I should continue with my Bach and late Beethoven and, after the concert (this was at one in the morning), he phoned me and said: 'You were right - you changed their religion]' '
Now, of course, with oft-quoted 'hype', the wide-spread commercialisation of 'classical' music, the CD explosion, extra radio coverage, etc, the musical world has changed. Or has it?
'Sometimes people say to me, 'Things were different when you began' - but they weren't. In fact, they were quite similar. There were too many pianists, too many performers, and not enough engagements. Young performers today are still asking the same questions: 'What shall I do to get engagements, how shall I find a manager, how do I get to play what I want to play?' Only now, there's a great deal of external brouhaha surrounding it all.' Tureck casts a disdainful eye on the concept of 'mere performing' and turns in preference to something far deeper - the devotion to music's spirit, its soul. But that, too, is beyond the practical reach of most students. How on earth can the modern-day, aspiring musician set his or her sights so high? Sacrifice is one answer - the sacrifice of time in the interests of art, because 'If there's no sacrifice, there's no art. There is much more commitment within the spirit of each human being than would appear to be in our world; but as the individual becomes more and more bombarded by the seductions and enticements of the externalising career, it gets destroyed. And when your career comes first, you're on very dangerous territory. So many young people who come to me want something less superficial. And I so understand them. I can remember the point when, after 15 years of maintaining 'two' careers, I asked myself if I really wanted to spend the rest of my life playing Chopin's G minor Ballade, wonderful work though it is. But I thought, no, I don't want that - I would rather live with the most profound music and ideas. I remember the very moment of that realisation, the room in which I was, and the place in the room - and I said to myself: I now know what I must do.'
So the pianist among the scientists continued her explorations into the intricate mysteries of Bachian counterpoint - measuring and tracing the heady adventures of Preludes, Fugues, Variations, and the astonishingly far-reaching harmonic implications of the Chromatic Fantasia and Fugue, the piece that closed her Friday evening lecture. To see her sit there, coolly engrossed in the terrifying Fantasia, with its eerie premonitions of 20th-century tonal disintegration, was one thing; but to hear her proclaim the Fugue, layer upon layer, with perfect clarity, poise and a chest-swelling grandeur that relegates all research back to the musical path-lab, reminded us that Dr Rosalyn Tureck's greatest claim on our attentions is the very quality that most defies analysis - her own artistry.
Rosalyn Tureck plays the 'Goldberg Variations': Tuesday 7.30 Wigmore Hall, London W1 (071-935 2141) pounds 10- pounds 15