'The finest player of the early piano' and 'a supreme magician among fortepianists' are but two of the accolades provoked by Andreas Staier's recent recordings. Certainly, few, if any, of today's early piano specialists rival Staier's flair and recreative imagination in, say, his Capriccio discs of Dussek sonatas (2/95 and 7/96) and his Teldec recording of the Schubert A minor Sonata, D845 (7/96). One clue to the freedom and flexibility of his playing lies in his enthusiasm for the great pianists of the early years of the century. 'When you hear recordings and piano rolls of Leschetizky or Moriz Rosenthal playing Liszt or Chopin, they sound as if they're composing the music themselves, playing with a kind of freedom, especially rhythmic freedom, which has nothing to do with a lack of respect, but gives a real insight into the music's inner function. Unlike so many modern pianists, who sound as if they're taking musical dictation, these older pianists play in musical gestures rather than individual notes. For me their playing is far more "authentic" than the mechanical interpretations you often hear today.' 

When we met at last September's Eisenstadt Haydn Festival (where he played a Mozart concerto on Haydn's newly restored fortepiano – 'an interesting experiment ' ), Staier had just recorded the last three Schubert sonatas using, as on his previous Schubert disc, an 1825 Viennese fortepiano by Johann Fritz, 'a specifically romantic instrument, on which it's far easier to convey the music's unique sense of fragility. All those intimidating dynamic markings – two pages of pianissimo, then decrescendo, then another pp. So much of his music is pianissimo, and with an early-19th century fortepiano you have so many more available colours in softer dynamics, than on a modern instrument. The una corda pedal, for instance, completely changes the sonority, giving a sinister, nocturnal colour, whereas on a modern piano it just makes the tone slightly softer. 

'At the other end of the spectrum, in a passage like the violent explosion in the slow movement of the A major, I use a lot more sustaining pedal than I would be able to do on a modern Steinway, which is an elephant by comparison. You can still hear the low chromatic bass, but it's a very harsh, ugly sound, just what Schubert's writing here implies. Then there are those places, as in the Andante of the B flat Sonata, where Schubert writes staccato with the sustaining pedal. On a modern instrument the instructions seem contradictory; but on the fortepiano they make perfect sense: short, delicate individual notes within an overall haze of sound.' 

Not surprisingly, Staier contemplated Schubert's great final trilogy with some trepidation. 'Every possible approach to this music seems to have been tried already. I agonized for a long time about whether I had something new and specific to say; but then I decided I must do them, because I've loved them all my musical life. The strange thing about them is that, except for the finale of the C minor, they 're not really difficult technically, but are impossible to play well. Some things have to be so infinitely precise, and there are often so few notes that whatever you do is already too much, too exaggerated or, especially, too loud. These sonatas are music which always make me feel a bad player!' 

Moving back from Schubert a generation or so, Staier has long been an enthusiastic advocate of the maverick Bohemian Dussek and of Clementi, famously dismissed by Mozart as 'a mere mechanicus'. 'Both composers spent much of their careers in England, which had a much more interesting musical life at that time than most people think. From the point of view of piano construction, and of keyboard style and technique, London was more progressive than Vienna. The English pianos produced by Broadwood and by Clementi's own firm were much more modern-sounding, more dramatic and resonant; and the great 19th-century solo virtuoso repertoire owes far more to Clementi, Dussek and their school than to Vienna. Clementi, who was really far more English than Italian, wrote some absolutely magnificent sonatas that can stand against anything Haydn or Mozart wrote for the piano, and from a pianistic stand-point are far more challenging. Like Haydn, too – and unlike Dussek, who was far more discursive – Clementi has a knack of saying a lot very economically. I would say that his F minor Sonata [Op 13 No6] is one of the greatest, most impassioned piano works of the 18th century.' 

Clementi and Dussek both feature in Staier's future recording plans for Teldec, though he stresses he has no 'encyclopedic ambitions' to record complete cycles of their – or anyone else's sonatas. Then, with Concerto Cologne, he will be exploring 'very selectively' the early Romantic concerto repertoire, starting with two pubescent concertos by Mendelssohn. 'It's fascinating to see how enormously fast he developed from the A minor Piano Concerto, written when he was 13, full of brilliant ideas but flawed in its overall design, to the E major Double Concerto written the next year, which is perfect. In the A minor Concerto he was experimenting with the kind of virtuoso writing he learnt from his teacher, Kalkbrenner, and sometimes he didn't know when to stop – a problem you also find in the enormous, garrulous first movements of concertos by, say, Hummel and Weber.' There will also be more Lieder – including Winterreise with Christoph Pregardien, with whom he has already made memorable discs of Schubert. 'Christoph's timbre has a clear, rather instrumental quality which blends very well with the fortepiano. Singers tend to be a strange species – all that ego and self-importance. But Christoph is not a typical singer. We've been working together for some years now, and there seem to be just the right creative tensions between us.' 

With the hour-glass rapidly running out we barely had time to touch on Staier's parallel career as a harpsichordist. But he will certainly be consolidating his reputation as an inventive, spontaneous exponent of Scarlatti with further discs of sonatas, and is hatching a programme of JS Bach transcriptions, including the A minor and the C major Violin Sonatas. 'The transcription of the A minor, probably by one of his sons, is complete, but the C major I have to do myself. Gustav Leonhardt, with whom I had some private lessons and who greatly impressed me with what I would call his analytical sensuousness, has already transcribed the sonata, so I'm probably rash to attempt it. But I have very different ideas from Leonhardt. His way was to elaborate the original as little as possible. But the harpsichord is such a different instrument from the violin. And from Bach's own transcriptions for harpsichord you can see how he adds counterpoints, not only to make the textures richer, but also to keep the rhythms flowing, which on the violin is not a problem. So the challenge for me is to decide which counterpoints to add where. As far as I know it hasn't been done before. Dangerous, I know, meddling with Bach, but I have to give it a try!'

Interview by Richard Wigmore