Music / Kronos Quartet Royal Festival Hall, London

As the first violinist rippled a bowl of water and swapped aggressive chants, the Kronos Quartet's latest commission began to take them somewhere new. It's more than two decades since Kronos launched out with a contemporary, American-based repertoire. In Britain, where comment and composing have been stuck in post-war European ways, Kronos pieces get a dismissive reception. No doubt they have become predictable, but the suspicion that people have misjudged the real action grows stronger. Why does this leading international group play next to nothing written here?

Lately it has started adding guest players from other musical cultures. The line-ups can look glib, especially on the "Pieces of Africa" tour. But the works themselves often do better than drafting in an extra, exotic layer to a fundamentally Western medium. Tan Dun's Ghost Opera, which the Kronos brought with them to the Royal Festival Hall on Tuesday, is the most sophisticated venture they have shown London so far. Tan, who had a high profile in this year's Proms (despite the non-performance of one scheduled premiere owing to a South Kensington power cut), belongs to the first Chinese generation that felt, belatedly, the impact of European modernism and came West to find out more.

He now lives in New York, where his music reflects a relationship of creative tension with the traditional and classical music of China. The Chinese side seems to be winning. Ghost Opera is still a Westernised piece in its overall form and its echoes of music-theatre works that did the campus rounds 10 years ago. Five musicians - the Kronos's guest is the American-based Wu Man, who plays the lute-like pipa - move around the stage and play percussion as well as strings. But there are Asian qualities and symbolic overtones to the chanting and the percussion: metal, water, paper, stones.

The shared musical ideas belong to China and the West, extending from folk-song and Bach quotations to freely melodic phrases and pulsing rhythms. They enable pipa and quartet to make musical conversation, sometimes poetic, sometimes fun: at one point the quoted Bach prelude detunes into a Chinese variation. Ghost Opera holds a delicate, provisional balance. It has gone much further than Western music with a Chinese accent, and not yet made the leap of taking what it needs from the West to make new, completely Chinese music. At the end, the pipa disappears and the Bach prevails. But the theatrical ambience lets a distinctive Asian feeling come through on the visual level.

The concert's first half was quite short, but felt long. Only one piece, Julia Wolfe's Dig Deep, fell into Kronos stereotypes, pounding away with contrasted ideas that gradually moved together - like a film in slow motion, despite the quantity of notes. John's Book of Alleged Dances, five pieces by John Adams, had their moments of ingenious wit as they wove their way round a shifting, recorded rhythm track. There was no shortage of quiet eventfulness in the more extended dances, and a touch of sweet melody in "Pavane", but they seemed to be sidestepping any real power of expression, and the overall dry, desultory impact drew cool applause. That left a traditionally romantic elegy, Song of 20 Shadows by Ken Benshoof, as the most rounded and effective of the night's quartet-only pieces. Viola- led, it had the warmest and most focused performance.

ROBERT MAYCOCK