TANGO Gidon Kremer QEH, SBC, London

As encore after encore rolled off the stage of the packed Queen Elizabeth Hall on the first night of the South Bank's Meltdown Festival, Gidon Kremer's smile seemed to indicate that he might cheerfully give up all the classics for the chance of playing the music of Astor Piazzolla. A new love seemed etched on his face, perhaps a strange one: a Latvian violinist hooked on an Argentinian's tango? But when did love or art observe boundaries?

It's an interesting quirk of fate that Piazzolla's nuevo tango should now be so feted by "classical" musicians. For it was Nadia Boulanger, that ambassador of "classical" modernist music, who packed the young Piazzolla back from Paris to Argentina in the 1950s, exhorting him to revolutionise the tango rather than mess with straight-laced serialism. No doubt she recognised his extraordinary lyrical gifts, gifts that could never have found expression within serialism's narrow confines.

In Britain, Piazzolla was hardly detected before his death in 1992 at the age of 71. His first appearance was at the Almeida in 1985; attempts at negotiating a UK tour for 1987 were thwarted by the after-effects of the Falklands war. In London, he played with a quintet comprising violin, double-bass, guitar, piano. Piazzolla himself was on bandoneon- the ultimate squeeze box - and very much the leader. The band had a roughness, an earthiness, through which the poignant cry of the bandoneon would course. Kremer at the Queen Elizabeth Hall with a three-piece band of immaculately trained conservatory musicians - Per Arne Glorvigen, bandoneon, Vadim Sakharov, piano, and Alois Posch, double bass - is the boss, and the balance of the group is changed by having the violin rather than bandoneon in the lead. If, at first, in the gloom of blue light, the playing seemed moderately straight-laced, by the time the encores started, the lights had come up, and a full camera crew was on stage, the music-making was loose and magical, the rapport between the players one of intimacy and fun. Kremer captured the spirit of Piazzolla to perfection - hinting at the roughness, tender with his tone, judging the hesitating slides perfectly - even though the smoke of Buenos Aires was nowhere to be found.

Piazzolla's fangos give an almost Cubist perspective to the form. The sensuality, raunchiness and melancholy of sweet bitterness sway over the syncopations of the tell-tale rhythm but there's always a surprise, an unusual harmony or colour - rasping behind the bridge, tapping on wood - or a turn from yearning sweetness to astringent insistence. The programme re-lived, in the main, the repertoire from their sensational CD, Hommage a Piazzolla. Even the Georgian composer Giha Kancheli provided an encore, a small jewel: "Instead of a Tango". He too is touched by the Piazzolla spell.