'Why be normal?'

Brazilian rockers Os Mutantes were poised to take over the world, but they collapsed under the weight of 1960s free love and drugs. Now they're back. By Will Hodgkinson
Os Mutantes
'Why be normal when you can go where the nuts come from?' ... Os Mutantes

There is a rich lineage of great musicians who have been discovered long after their due. The Buena Vista Social Club took 40 years to find an audience outside Cuba. When the English singer Vashti Bunyan released her debut album in 1970, it was met with such deafening indifference that it took her 36 years to get round to recording a follow-up. Had Nick Drake known that his dismal-selling albums from the early 1970s would become cult classics, he might still be with us today.

But perhaps the most dramatic revival story belongs to the Brazilian psychedelic band Os Mutantes. Formed in 1965 by Arnaldo and Sergio Dias Baptista, teenage brothers from Sao Paulo, and Arnaldo's girlfriend Rita Lee, Os Mutantes were Brazil's most inventive and irreverent rock'n'roll group. The trio became the backing band for Tropicália, the avant-garde movement formed by the singers Gilberto Gil and Caetano Veloso in 1967, but in the mid-1970s the band fell apart - not least because the two brothers argued over, of all things, guitars. By the 1980s, Os Mutantes had become a footnote in Brazil's history; outside Brazil, few got to hear of them at all.

"What has happened to Mutantes?" says Veloso, when I ask him about his old friends' late-flowering international success. "Everyone has gone crazy over them! When Gil and I were in England in the 70s, we would play people Mutantes records and the reaction would always be the same, 'It sounds like a Beatles rip-off.' We knew they were much more than that, but nobody else in England did ... until now."

Two decades after the band fell apart, the Baptista brothers are back together, rehearsing at Sergio's studio on the outskirts of Sao Paulo for next week's Os Mutantes concert in London. It will be the first time Os Mutantes have ever performed outside Brazil, and the first time the brothers have shared a stage since 1975. After that, they will be travelling across the US for a tour that is already mostly sold out. The US singer Devendra Banhart, a substantial name himself, wrote to Mutantes and asked if he could be their roadie. (They made him a support act for the London show.)

"It's been so great," says Sergio Dias, a toothy, cheerful, fiftysomething rocker who looks rather like a Brazilian version of Paul McCartney. "We've been working hard, Arnaldo is sounding better than I've ever heard him, and we're getting on so well. I asked God for a reconciliation with my brother because all of this bullshit between us had been going on for too long. And you know what? It happened!"

Sons of a poet father and a concert pianist mother, the Baptistas brought a deep musical knowledge and a literary grounding to a love of the Beatles that inspired them to form a band. The latter they shared with Rita Lee, the rebellious daugher of Italian-American immigrants. Together, they would perform Beatles songs with an orchestra on Brazilian TV, and it was here that they met the classical maestro Rogerio Duprat. He introduced them to the singer Gilberto Gil (now Brazil's minister of culture), who made Os Mutantes part of the Tropicalia movement. When Gil and Veloso were jailed and then exiled to England by Brazil's military dictatorship from 1969 to 1972, it was left to Os Mutantes to lead the country's psychedelic revolution, providing the hippy underground with its own anthem, Ando Meio Desligado (I'm Feeling Spaced Out). But they collapsed under the weight of free love and drug use in the years that followed.

Rita Lee left in 1974 to become a solo artist of stadium-filling popularity and questionable artistic merit, while Arnaldo Baptista had mental breakdowns; his brother Sergio worked as a session guitarist in the US. The brothers fell out (Arnaldo said that it was because Sergio liked Fender guitars while he favoured Gibsons) and by the 1980s Os Mutantes were either forgotten, or thought of as Rita Lee's old hippy band.

Why the revival? Mutantes became a hip name to drop after endorsements by Beck and Kurt Cobain in the early 1990s, but the cult only really got going after the 1999 release of Everything Is Possible!, a compilation put together by David Byrne on his label Luaka Bop. On the cover was a picture of three freaky teenagers joyously jumping in the air; the inner sleeve showed them dressed as aliens - and the music was equally intriguing. Ave, Lucifer was a tender, poetic ode to Satan while a cover of the Brazilian singer Jorge Ben's O Minha Menina (My Girl) turned the samba rock of the original into a garage-punk classic through the use of a bizarre effects pedal powered by a sewing machine, built by Sergio and Arnaldo's elder brother Claudio.

This inventiveness was at the heart of Os Mutantes' creativity. Frustrated at the lack of decent musical equipment in 1960s Brazil, the band had no choice but to find ways of re-creating the backwards tape sounds they heard on the Beatles' Tomorrow Never Knows (by aiming a can of bug spray at the microphone) and Jimi Hendrix's wah-wah pedal (Claudio's wooh-wooh, which made Sergio's guitar sound as if it was going to be sick). Everything Is Possible! got the message out: while the Beatles and the Stones were making history, three teenagers from Brazil were fighting the twin forces of a military dictatorship and a lack of resources with surreal humour and ingenuity.

The fact that Rita Lee isn't playing with the Baptista brothers is a sign that not everything is resolved. Lee and Arnaldo Baptista met in 1964, both aged 16, at a high-school battle of the bands in Sao Paulo. They became sweethearts and, with Sergio on board, Os Mutantes were born. After Rita Lee stole the keys to the wardrobe departments of the TV shows they were appearing on, Os Mutantes' theatrical image was born, too. She would dress the band up as conquistadors for one appearance, witches for the next. "Everyone came to me for ideas," says Lee. "Why be normal when you can go where the nuts come from?"

The good times were not to last. Sergio dates the beginning of the end to the time Arnaldo took off on a motorbike across South America in 1970, leaving Lee behind. He returned to marry her on December 30 1971, the day she turned 24. The marriage was over by the time she was 25.

"I didn't leave. They chucked me out!" says Lee of her 1974 departure. Arnaldo, whose heavy LSD intake in 1971 was already affecting his mental health, remembers it differently. "Rita Lee put me in the madhouse." Why? "Because she wanted to go to Europe. I went to the madhouse five or six times over the next 10 years, and I was somehow disconnected with the world and I wanted to get out. So I jumped."

In 1982 Arnaldo attempted to escape from a psychiatric institution by jumping from a fifth-floor window. The fall put him in a coma for six weeks, but he emerged from it with his future wife Lucinha - a fan who had read about the fall in the press - by his side. Since then he has been making a slow recovery, living quietly in a small town in the state of Minas Gerais. He is philosophical about the forthcoming concert. "I am happy to be making music with my brother again. Maybe it doesn't matter that Rita Lee isn't doing it because we have this new girl now." (She has a name, too: Lia Duncan.)

The London concert fulfils a long-gestating dream of the Baptista brothers to play in the land that inspired them in the first place, and Sergio has been digging out Claudio's old contraptions to re-create the unique Mutantes sound. Until recently, the Baptistas were unaware of the cult that has been building up around their old band. "I didn't even know that we were booked to do the concert," says Sergio. "Nobody told me! The whole thing seemed to happen naturally, like a spontaneous combustion. At first I was pissed off. Now I think it's great because it would never have happened if it had been left to Arnaldo and me. In fact, it's some kind of a miracle".

· Os Mutantes play the Barbican, London EC2, on Monday May 22. Box office: 020-7638 8891.