Mullova/Bezuidenhout, Queen Elizabeth Hall, London

The crowd that came to hear Viktoria Mullova open her "artist in focus" series was as heterogeneous as you'd expect, given the scope of this statuesque star's activities. Her recital on period instruments was to be followed by a concert with her own ensemble, and also by an uncategorisable event in which she and her "crossover" friends would purvey their rich brew of Hungarian Gypsy-plus-jazz. If she didn't exist, you'd have a job inventing her: the key to her art lies in what she has come out of.

She began life, goaded by her ambitious parents, as an infant fiddler in Moscow, and though her obsessive perfectionism took her to the heights – winning the Tchaikovsky competition in 1982 – the Soviet straitjacket blighted her life. She once told me, "One careless word could cost you your liberty, and one careless note could damage your chances of artistic success." Hence her daring defection to the West at the height of the Cold War; hence her determination to play the kinds of music that had been forbidden her. It was her good fortune that the man she ultimately married – the cellist Matthew Barley, with whom she now plays jazz – should turn out to be one of classical music's leading mould-breakers.

The funky African outfit in which she appeared contrasted piquantly with the mellow sound created by her gut-stringed Guadagnini and Kristian Bezuidenhout's fortepiano, as they launched into Schubert's Duo Sonata in A major. But as they sailed through this graceful work, followed by the Rondo brilliant, one was struck by the sonic balance between their instruments: infinitely more satisfying that the usual mismatch of Steinway and Strad, where the latter is always in danger of being obliterated by the former.

When they returned, however, to deliver Beethoven's Violin Sonata in E flat major, followed by his "Kreutzer Sonata", we saw what these musicians are really made of. Mullova's immaculate playing gave off a lovely sense of respiration, while Bezuidenhout made the fortepiano sound more beautiful than I have ever heard it before.

And if that was a revelation, so was what they did with Beethoven's most overplayed violin-and-piano work. The outer movements of the "Kreutzer" had all the force you could wish, with the piano rippling and roaring while the violin effortlessly asserted its dominance; the majestic slow-movement variations were, simply, inspired.