Egberto Gismonti tells Phil Johnson his musical tales of Brazil
Ah, but is it jazz? The traditional complaint of purists everywhere was always going to be tested by the strange case of Egberto Gismonti. Indeed, the Brazilian composer, guitarist and pianist - who begins a Contemporary Music Network tour next week in the company of the Electra Strings, the all-female mini-orchestra from, among other things, Jools Holland's Later - could have been invented especially to enrage and confuse people who like their music to come in neat little categories. Gismonti has made more than 60 albums, written for classical orchestras, for film and for dance, but in performance he's most often seen playing various types of home-made or adapted guitars, mixing elements from both the high and low cultures of Brazil into a unique combination of indigenous folk forms and the classical school of Brazil's most famous composer, Villa-Lobos. His British tour includes both solo improvisations and the premiere of a new work for strings.

Gismonti, who is 51, studied piano and composition for 15 years before training in Paris with Jean Barraque and Nadia Boulanger in the late Sixties, returning to Brazil in 1971 after Boulanger encouraged him to discover his own roots rather than copy European models. Accordingly, he abandoned the piano in favour of the guitar, inspired by Django Reinhardt and Jimi Hendrix, and then spent a period living with the Xingu Indians in the Amazon. "In general, the composers in the 1960s and 70s, if you're talking about Stockhausen or even John Cage, all these guys were very intellectual," he says. "But they were far from a basic art - to say something rather than to think about something. People like Anton Webern and Jean Barraque, who spent a lot of time with him, taught me a lot but by studying Brazilian music I tried to find a music that was much more natural than this intellectual stuff."

Gismonti's breakthrough, and his first album for the German label ECM in 1976, was the incredible Danca Das Cabecas, which proved to be a kind of musical equivalent to South American magic realism in the novel, and a revelation for listeners to whom the concept of World Music did not yet exist. Accompanied only by the percussion of Nana Vasconcelos, Gismonti's guitar created a whole world of sound that was quite unlike anything heard before. "It's about two guys walking through the jungle," he says. "Sometimes it's very humid, sometimes very dry, sometimes full of animals and sometimes full of silence." Ah, but is it jazz?

It's certainly not the mellow, sand-between-the-toes, sound of Brazilian bossa nova as popularised by Jobim and Gilberto. Although Gismonti wrote an album for Airto Moreira and Flora Purim in 1975 in Los Angeles, his music is a long way from most received notions of jazz, whether Brazilian or not. And although together with other ECM artists like the late Don Cherry and Jan Garbarek, he helped pioneer a new kind of improvised music that took folk forms rather than American songs as its inspiration, he refuses to accept the jazz label. "I should say that jazz is very important for one kind of Brazilian music, bossa nova," he says. "If you're thinking about how much bossa nova is used by American musicians, there is a big connection in terms of chord changes, harmonies and this kind of stuff. But basically, there's no connection if you think about the time signatures and the fact that jazz is in four and Brazilian music is in two. Of course, musicians like music, and there are a lot of jazz musicians who I like, but I'm not able to play any kind of jazz. I do it for fun, yes, play a little jazz with my kids or with other musicians, but not to represent myself."

In performance, Gismonti is as singular as he sounds, with wild long hair cascading from a hat or escaping from the ties of his pony-tail, moving from one stringed instrument to another, and from guitar to piano, with a sense of energy and purpose that can leave his audience feeling exhausted. For many of his fans he is, most of all, a guitar-hero, with a technique that is famously impossible to duplicate. This is at least partly, he explains, because although he was an accomplished pianist, he taught himself to play guitar in isolation.

"Where I was living at the time was a city 300 kilometres from Rio called Friburgo. They had a lot of people playing guitar but no teacher, and I didn't know anything about the classical, six-string instrument. The first guitar I had had seven strings, which was very useful for the Brazilian music called Choro - that's where the instrument plays all the bass-lines. After six months or a year of doing transcriptions from piano, I realised that I was missing a lot of notes on the high and low registers and someone gave me the idea of adding one more string, so I had an eight-string. Because of the piano training, I was used to using two hands independently and I use that on the guitar."

Gismonti's technique has developed alongside a continually deepening interest in the culture and people of Brazil, and each of his albums, he says, is an attempt to tell a story. "I'm trying to have a Brazilian cultural history for each one and trying to work or design or write a sort of Brazilian way. This is such a mixed country - there are Europeans, Africans, Brazilian Indians - that we're allowed to have all these contradictory stories. What I'm doing is presenting a very small part of my country, talking about all these stories."

And if you want to know where to find Gismonti's albums in the record store, try looking under Jazz first. It may not be an entirely accurate description, but it's as good a place as any.

Egberto Gismonti featuring the Electra Strings: St George's Brandon Hill, 0117-923 0359, Wed; Sallis Benney Theatre, Brighton, 01273 709709, Thur; RFH, London, 0171-960 4201, Fri; Turner Sims Hall, Southampton, 01703 595151, Sat; Great Hall, Dartington, 01803 863073, Sun.