Classical music: Time catches up with Kronos

It's astonishing to think that one of the world's finest and certainly almost pioneering string quartets - the redoubtable Kronos (right) - celebrates its 25th anniversary this year. But it does; and, since those days in the early 1970s, when they started operating out of leader David Harrington's one-room apartment, Kronos has gone on almost single-handedly to revolutionise the quartet genre during the last quarter of a century.

"At the time we started, most composers weren't writing quartet music any more," says Harrington. "It seemed to be a dead art form - well, if not quite dead, at least dying off. So, right from the start, we simply activated a policy of getting more composers to write more quartets." It's a policy which has brought about a gamut of exciting new music; Kronos's active commissioning process has yielded a staggering 400 new string quartets from composers spanning at least four generations, from six continents

Yet, for the seemingly eternally youthful and laid-back Harrington and his no-less-illustrious trio of compatriots - John Sherba, Hank Dutt and Joan Jeanrenaud - the desire to carry on with their great work seems as vigorous as ever. "Kronos is very strong at present," comments Harrington. "It seems the more music we play, the more we want to play; and the more and varied imagery we have to work with, the more questions there still are to answer. But, above that even, we relish performing together as a close-knit team and communicating with an audience."

Kronos continues to prove it is perhaps the string quartet that most others don't reach when they round off their current South Bank visit with two highly contrasting concerts in the Royal Festival Hall today. To begin with, at 2.30pm, the foursome delivers its first European performance of their recently devised "Kronos for Children", giving children as young as seven a chance to make music alongside the quartet. "Again, to get our audience excited and involved in the music we make has always been a key Kronos brief," comments Harrington, "be that Feldman, Reich or Gorecki, on the one hand, or simple but appealing tunes on the other. In Kronos for Children, we've worked with instrument-builder Craig Woodson; each member of the audience will receive a plastic box, a cylindrical pipe and a length of fishing line. Out of those simple materials they can then make what we call a 'drumpet' - an instrument that can be plucked, percussed or blown down. The concert ends with a riotous composition for Kronos and massed drumpets."

Then, in the evening at 8pm, yet another new and radical Kronos collaboration is in the offing when the foursome teams up with the legendary Romanian gypsy band Taraf de Haidouks. "Taraf de Haidouks is one of my favourite groups," says Harrington. "They have this passionate earthy sound which veers, dangerously, between melancholy and ecstasy."

In a short first half, Kronos sets the gypsy scene by playing Bartok's pithy 3rd Quartet, which draws on Eastern European folk themes, as well as music by the currently cultish figure of Astor Piazzolla. After a set from Taraf de Haidouks, the two groups come together on stage. "It's yet another challenge for us," concludes Harrington, "but we have some interesting material to share and air." It's yet another potentially enthralling manifestation of the global village of music-making that Kronos, now celebrating a glorious Silver Jubilee, has helped so much to engender.

The Kronos Quartet perform Kronos for Children (2.30pm today) and with Taraif de Hadouks (8pm tonight) at the South Bank Centre, SE1 (0171-960 4242)