An entire recital of one kind of piano piece might not seem a thrilling prospect, but Emanuel Ax's programme of wall-to-wall Ballades, interspersing romantic classics with two specially commissioned premieres, proved exceptionally fruitful. Invented by Chopin, the piano Ballade is a tough genre to pin down - driven by a narrative compul-sion rather than harmonic logic, they seem to tell a story, although their composers might not always have had any particular tale to tell.

There was definitely a fairy tale behind Chen Yi's slight but likeably evocative Ji-Dong-Nuo, which takes its name and inspiration from a Chinese folk ballad. A unison beginning opens out into short, animated passages largely based around the eastern five-note scale, moving through mercurial changes of mood and finally melting away into happy-ever-after nothingness. Kaija Saariaho seemed more reluctant to play the game: with few narrative elements, her new Ballade could have taken just about any title. It began with a grand arabesque that left Ax's hands far apart, and it took a sonorous sweep down the keyboard to bring them together again. The rest of the piece took up this idea of lines separating and coalescing, with Ax working hard to bring out the melodic line from within the dense figuration.

While it was good to see an artist commissioning new music, Ax's finest playing came in the classics. In Brahms' four Op. 10 Ballades and Liszt's Ballade No. 2 in B minor, he spun seemingly endless melodic lines, occasionally smudging some detail through liberal application of the sustaining pedal, but more than making up for this with the sheer sense of shape and musical architecture his playing revealed. And in Chopin's four Ballades he managed to make even the most decorated writing seem entirely purposeful and essential.