Piazzolla's career embodied those same tensions: born in Argentina in 1921, he moved to New York as a child. There he became a virtuoso performer on the bandoneon, the serpentine wooden accordion that plays a central role in tango, both new and old. At the age of 13, he was invited to tour Latin America by tango superstar Carlos Gardel. Piazzolla never made the tour, in the course of which Gardel died in a plane crash, but he was soon back in Argentina, playing in the band of Anibal Troilo, who left Piazzolla his bandoneon when he died. Yet he had ambitions to become a serious composer. He studied for a while with Alberto Ginastera before, in the 1950s, a government grant sent him to Paris to study with Nadia Boulanger, who had already helped composers as diverse as Elliott Carter and Lennox Berkeley to find their creative voices. With characteristic directness, Boulanger advised Piazzolla to stick to what he did best. He returned to Argentina, and the rest is nuevo tango.
Piazzolla's innovations took the music closer to jazz than to classical music, and at different times he collaborated with jazzmen Gerry Mulligan and Gary Burton. Now, though, his music has thoroughly penetrated the concert-halls that Boulanger said he'd never enter. This weekend, the Latvian violinist Gidon Kremer, one of the most respected figures in classical music, brings his Astor Quartet to London to perform a programme of Piazzolla's music. Meanwhile, the Spanish conductor Josep Pons is enjoying chart success on both sides of the Atlantic with his recording of Piazzolla's Concierto para bandoneon. Neither Kremer nor Pons claims any expertise in tango as a whole; indeed, Kremer goes so far as to say that "Piazzolla took tango out of cheap places, where it was just an entertainment, popular tunes in a coffee shop. His music is of a higher quality. I don't reject the roots of tango, and there were many wonderful tangos written before Piazzolla, but he works with more sophisticated material, the emotion in his music is more profound."
When I suggest to Pons that, for many, Piazzolla's willingness to write for classical orchestra betrays the essential nature of tango, he leaps to the composer's defence. Comparing Piazzolla's use of tango with Bartok's researches in folk music, he goes on: "True, tango has popular roots, and Piazzolla had a classical training with Boulanger, but he also knew the ways of tango, and not only its ways but also its spirit. He uses the music to express his own ideas, grafting on to it knowledge he had of other musics. Is that betrayal? I'd say it's enrichment, evolution. If popular music doesn't evolve, it becomes a mere museum of dead objects. And when it comes to performing Piazzolla, you have to find the particular interpretative style just as much as you do with, say, Rossini or Stravinsky. It's a question of balancing the elegance of the classical orchestra with the passion that is tango: the exaggerated rubato, the accents, the wild treatment of rhythm. When you feel the rhythm, you want to dance, but this is much more than dance music."
Gidon Kremer likewise emphasises the importance of style, and rejects any suggestion that, in playing Piazzolla's music, he's slumming it: "I feel as much at home in Piazzolla's world as in the world of the great composers of the past. You immediately sense if someone plays him in a way that's overly sentimental, too simplified or aggressive. It's difficult to get it right: but isn't it so with Mozart? I'm not ashamed of making that comparison. Piazzolla is not easy, or banal or naive. He's a wonderful composer and deserves the best treatment."
Kremer admits that it took time to come round to the idea that he might actually perform Piazzolla: "Many years ago, I saw some videotapes of his performances, then I had the opportunity to see him perform in Paris, about 12, 13 years ago. I never imagined I would play his music, I was simply overwhelmed by its energy, its sincerity, its virtuosity. It lit a fire in me. Then, a couple of years ago, a colleague suggested that I play some of his music. I was sceptical, but I took a look at some arrangements, and they just fanned the flame. Soon after, I played a piece in concert with the pianist Martha Argerich, then I played another piece with some Moscow musicians, and eventually, about two years ago, I put together a whole evening of Piazzolla. That finally proved to me that I could play this music."
One problem Kremer faces is that the music was not written for his quartet (Kremer's violin, plus bandoneon, piano and double bass), but for other combinations, and so requires new arrangements, either by performers, or by other composers: "Piazzolla left structures, he left harmonies - everything is available, but you have to fill it with your own inventiveness. Some of our arrangements are based on his, some are commissioned from composer friends of mine, like Sofia Gubaidulina and Leonid Desyatnikov, but most of it is our own work. Piazzolla started as an orchestral musician, then slowly he pared it down, to a nonet, a sextet, and then finally, for his best recordings, a quintet. We reduced it even further, to four. I'm not saying it's an improvement, simply that the presentation we're looking for can be found in a quartet. Anything additional is, for us, an embellishment. The music allows you space to improvise. Now I was never educated in improvisation, but his music demands at least a minimum of it. It's more exciting when it's unpredictable, it's about expressive freedom, and in keeping pace with his bar-lines, we allow ourselves room to fly."
There, perhaps, is the appeal of this music for so many classical performers. The only opportunity to fly that usually comes their way is the trip from one capital city to the next as part of the superstar circuit. Piazzolla's music allows them to break free from routine, to find new challenges, new audiences. Kremer plans eventually to take his Piazzolla show to Latin America. That really will be the acid test of his new nuevo tango nuevo.
`Le Grand Tango' 7.45pm Sat, QEH, London, SE1. Booking: 0171-928 8800; Kremer's `Hommage a Piazzolla' is on Nonesuch Records; Pons's `Bandoneon Concerto' is on Harmonia Mundi