Even more, perhaps, than the solo piano music, Mozart's piano duet works, with their inevitably rather thick and low-pitched textures, can benefit from the lightness and the tonal transparency of the fortepiano. The present recording, like the solo one that Andras Schiff made in 1991 (5/92), uses the instrument in the Mozart Geburtshaus in Salzburg, ascribed to Anton Walter and traditionally (but without real evidence) claimed as Mozart's own instrument; whether that is true or not, it is the kind of instrument that he would have used although I suspect this one has been fairly thoroughly restored. At any rate, I have never heard, on a modern grand, half as much of the fascinatingly intricate textures of the first movement of the great K497 Sonata or the clarity of line in the Andante, nor the glitter and brilliance these players provide in the passagework of the C major Sonata, K521. And possibly the best of all here is the charming set of variations, K501, its theme so expressively shaped and its elaborations so gracefully articulated. The two fantasias have a finely sombre ring, although there is nothing specially authentic about that as the works were written for mechanical organ.
I am not quite sure, however, of the extent to which these players—a modern, Bosendorfer-accustomed pianist and a renowned harpsichordist and organist—are really exponents of the fortepiano. The fortepiano, like any other instrument, requires familiarity; you cannot simply play it with a modern piano (or harpsichord) technique and expect to get the best out of it. It has a technique of its own, and a rather limited dynamic range to which a player needs to tune his expectations. To play forcefully on it with anything like the weight one would bring to a modern instrument does not simply make it louder; it produces a somewhat brittle and clangy quality of tone. I fear that is what sometimes, indeed quite often, happens here. The accents in the first movement of K521, a vigorous and large-scale piece, are too violent, and the louder music does not emerge simply as loud but as explosive and even coarse in tone. The Andante of this sonata seems to me distinctly lacking in poetic feeling and I thought the finale (in any case not one of Mozart's best) rather stilted in style. The noble Sonata in F certainly benefits, as I have indicated, from the clarity of the fortepiano though the playing here seems rather relentless. I should have liked more flexibility in the slow movement, which does not yield all its expressiveness in this performance, and again in the finale where there is a lot of heavy playing.
In short, marvellous though it is to hear the music on an instrument with such claims to authenticity, with all the fresh insights it allows, it might have been wiser for Decca and the Internationale Stiftung Mozarteum to entrust such recordings to performers perhaps less glamorous but better versed in the handling of a sensitive old instrument—and no doubt the ISM have given due thought to the irreversible wear and tear that this kind of handling must involve.'