LSO/Chung/Andsnes, Barbican Hall, London

Did that really happen? Was I there? Word was out of a strong new Grieg Piano Concerto recording by Leif Ove Andsnes, but it was something else altogether to witness him perform the old warhorse along with a conductor who could strike sparks off a piece of Playdough. So familiar is the music that it is hard for listeners to encounter it without lapsing into cosy mode, let alone a pianist on what amounts to a promo tour. Andsnes did it, though; he played the Grieg so that it will be talked about for years.

The magic began as soon as the London Symphony Orchestra's woodwind, then the violins, shaped the opening tune persuasively, just inviting the next musician to listen, digest and respond. That is what you would expect to happen in most kinds of music, but not often with classical soloists. They have learnt the score by heart and they play it their way, and most of them cannot adapt, or do not bother to, at least that early in a performance.

With Andsnes the sense was as if he had just heard it for the first time and played it back to the orchestra as the next stage of a conversation.

It happened again when he picked up on the way Myung-Wha Chung conducted the cellos through the next melody. He did not have to mess it around, in the fussy way that some soloists do in the belief that it will put their personal mark on a well-known piece; the playing was forthright and direct. Nor did he interfere with the heightened, midsummer-night-sun mood of Grieg's slow movement. But there is simplicity and there is virtuoso simplicity.

In the finale, however straightforward the dance rhythms, Andsnes articulated the keyboard display with a brilliance, speed and power that kept the audience on the edge of their seats. They yelled for, and got, an encore, a turbulent piece of Schumann that sounded as though the performer were improvising it for himself.

The Fifth Symphony of Mahler was not quite another performance of your dreams, but in any other context it would have been the main event. Chung judged tricky changes of pace, moments like the wind-down from the frantic centre of the opening funeral march, which often lurches back to the basic slow gait but here, prepared earlier than usual, ran on with continuity intact. Anticipation was the trick with the sustained intensity both times the big chorales approached, keeping it slow the first time and letting the pace run on at the end of the symphony.

The one disappointment was slow quiet music, including the Death in Venice movement for strings, which remained static and self-conscious and did not find the easy flow that Chung had given to Grieg's melodies. All in all, though, a stirring night. When one of London's orchestras is up for its next principal conductor, Chung has to be a contender: he is an obvious hit with the musicians, and for listeners it is a revelation every time.