Charles Rosen, Queen Elizabeth Hall, London <!-- none onestar twostar threestar fourstar fivestar -->

The consummate writer, critic, musicologist and pianist Charles Rosen has been at the forefront of his many fields for most of his 80 years. To a packed hall, he gave a programme that would tax the greatest performers half his age, in Beethoven's Appassionata sonata Op 57 and the Diabelli Variations Op 120. From the opening of Op 57, Rosen cast a spell of mystery and tension, of a vision understood. This set the pattern for the evening.

Rosen's fingers nowadays may not quite keep up with his brain, but we know what he is trying to convey. Here is a musician who has lived and breathed Beethoven for so long. That the pedal occasionally smudges torrents of notes is beside the point; Rosen knows what needs to be heard - in particular, harmonic and contrapuntal voicing that so often surprises - and he makes it heard.

If the slow movement of Op 57 was hardly indulgent - there was no hanging about, no egotistical flamboyance - the sound was rich and unveiling. Tenderness and poignancy ranged over this rendition, but it brought to mind Schnabel's remark that no performance could be as great as the work itself.

The previous evening, Rosen had given a 100-minute talk (without notes) entitled "Beethoven's Ambition", which had ranged widely but came to focus on the Diabelli Variations - at its time, the longest piano work ever written. As he pointed out, Beethoven had taken a great deal from Bach, in particular the Goldberg Variations, and in many ways set out to compete with it.

Diabelli had called on 50 composers to write variations on his trivial waltz, to be published in aid of war widows and orphans from the Napoleonic wars. Beethoven responded by writing not so much for audiences or performers, but for composers.

The Diabelli Variations is a primer, a conspicuous showing-off, to demonstrate what could be done with a theme. At its considerable length, it was never intended to be played in public. Beethoven transforms Diabelli's "cobbler's patch" by parody - Mozart, Handel and Bach - and by reduction where only a harmonic framework survives.

Rosen is brusque as a speaker, and so was much of his playing. But the great Bachian 31st variation melted hearts. A Chopin waltz ended the (three) encores. A historic occasion.