Hélÿne Grimaud, Royal Festival Hall, London

You can generally divide musicians into "top down" and "bottom up".

You can generally divide musicians into "top down" and "bottom up". The former are the ones who conduct the tune instead of the orchestra, and virtually all opera singers. The latter are those who build their music on a fundamental bass-line, including many jazz musicians. Hélène Grimaud seems to be of a rarer sort that hears music from the middle out. What's going on at the centre of the piano keyboard, particularly the upper reaches of the left hand, is essential to the way she plays and the sound she makes.

It's an attitude often shared by pianist-composers. Think of Rachmaninov's recordings; and you can imagine Mozart - who liked to play viola in string quartets because it put him in the middle of the action - doing something similar. Grimaud may restrict herself to playing other people's music, but she gravitates to those who had careers as pianists. In this London recital, she performed two of the greatest, Chopin being the one she has come to more recently. From the start of his Barcarolle, in a remarkable performance, she showed a fresh approach uncluttered by current norms.

Of all the piano-composers, Chopin is particularly tempting to tune-and-accompaniment merchants, but there was none of your romantic gondola serenade about this presentation. The music surged on, urgent and lucid and often forthright, propelled by its layers of counterpoint, transforming the left-hand pulse from conventional accompaniment into the stark, repetitive motor of the music's build-ups.

There's another side to Grimaud's playing: radiant, exploratory and fantastic. It came into its own in the Berceuse and illuminated the oases of stillness in the central movements of the Sonata in B flat minor, which were like unsentimental memories of lost happiness. Around them Grimaud drove the music powerfully, once again turning apparently supporting figures into elements of an equal dialogue. In the finale, fleet and surreally quiet as it should be, there was a moment of understated shock as she changed pedal tactics to delineate the hint of a climax.

All this passionate, sometimes severe, clarity left an appetite for hearing Grimaud play Bach. Instead there was Rachmaninov, in deference to her new CD. As a concert experience, this produced a surfeit of the key of B flat, mainly minor, but the Rachmaninov Second Sonata is one of her star turns - she has recorded her own mix of the composer's two versions - and the work is not exactly overexposed. Her championing of it was well worthwhile, as she made the music both heady and pithy.

This is where her way of playing Chopin comes from, because the manner was much the same, although with the later composer it was more conventionally idiomatic.

Barely pausing for breath, Grimaud swept through three encores with increasing spectacle and vivacity to the ear, and with not one uneconomical movement to the eye.