Classical: Till Fellner Queen Elizabeth Hall, London

Till Fellner is 24, the same age as Julius Reubke when he died in 1858. Reubke is known to every organist as composer of the 94th Psalm, one of the greatest works of the Romantic period - a unique single-movement sonata, gloomy and heroic. His Piano Sonata is much less well known, at least in this country, and the small German firm which published it has gone out of business, so you can't even buy the music. There are two recordings available here, but Farringdon Records in the Royal Festival Hall foyer let the St Matthew Passion and Lesley Garrett take up all the space in their racks reflecting South Bank events: "This is our busiest weekend," they told me, "so we sent the Reubke back to Germany." The CD to go for is Claudius Tanski's, on Dabringhaus & Grimm, which also has the 94th Psalm - at least, until Fellner's own promised recording arrives.

That will be interesting to hear, because in the Queen Elizabeth Hall on Sunday afternoon, he seemed distinctly to economise on volume in the stormier passages, which, if his playing altogether had not been so thoroughly accomplished, so sheerly beautiful, would have made one feel emotionally short-changed. A little underpowered, yes, but his performance was certainly not short of commitment, and frankly, when a pianist is such a thoroughbred, so completely in harmony with the instrument, I am not inclined to complain.

As for Reubke's Piano Sonata itself, there ought to be no doubt about its genius. For a start, it speaks the most advanced musical language of its time with absolute consistency. The brooding character and harmonic colour of the opening is very like the organ sonata, but despite the profusion of double octaves, which Fellner played very lightly, Reubke's piano textures are leaner than Liszt's in his Sonata of three years earlier, while Reubke's mode of continuity is more supple, less windy; nor does he resort to a sham fugue - or any sort of fugue at all. Many composers die without achieving the sense of narrative pace which to Reubke seemed to come naturally, and the whole atmosphere he creates is marvellously picturesque, in a way which would not have seemed outmoded had he written the music at the end of the 19th century.

Fellner was very clever to precede Reubke's great work with Mendelssohn's deliciously transparent Variations serieuses and a whole first half of Mozart - the Rondo in A minor (which Mendelssohn called the most perfect rondo ever written), the Sonata in B flat, K333 and the Variations on Unser dummer Pobel meint. They were all given performances on the most distinguished level, as decisive as they were sensitive. You could sense the pleasure Fellner took in his own ease, the savouring of many refinements of phrasing and nuance. Let's hear him in some concertos by Mozart soon.