Kurt Cobain once sent Os Mutantes a fan letter

Sergio Dias is the lead singer and founder of Brazilian band Os Mutantes.

The late 1960s in Brazil produced an explosion of new sounds and ideas that still reverberate throughout the world.

During that time, Os Mutantes' creative cannibalism produced psychedelic gems unlike anything else in the world.

They were exactly what their name implies: a mutant genetic recombination of elements of John Cage, The Beatles, and Bossa Nova.

Along with Gilberto Gil and Caetano Veloso, Os Mutantes was part of the Tropicalist movement, which emerged in Brazil in the late 1960's, intent on bringing electric instruments and rock influences into Brazilian popular music, no matter who might be offended.

With their cut-and-paste, collage mentality and their penchant for irony, the Tropicalists defined an aesthetic that dominates much of today's pop music.

Os Mutantes was the first major rock group in any country to have a truly international sound that mixed psychedelia with Latin rhythms, avant-garde classical elements, found sounds, studio technology, surrealistic lyrics and sampling and the group's vanguard reputation remains, especially among younger foreign listeners, who came to Os Mutantes long after its heyday.

To hear the four albums the group released between 1968 and 1972 is to encounter not only songs that nowadays would be called deconstructions of Brazilian classics, but also ballads that are precursors to Queen, bluesy parodies of Janis Joplin and hints of Santana and Frank Zappa.

Kurt Cobain was so much of an admirer of the group that when Nirvana played in Brazil, he sent a fan letter to Arnaldo Baptista, the Mutantes's gifted keyboard player. But the contemporary foreign artist who perhaps most identifies with the Mutantes sound and the group's "anthropophagic" aesthetic is Beck.

'Hearing Os Mutantes for the first time was one of those revelatory moments you live for as a musician, when you find something that you have been wanting to hear for years but never thought existed," he said in an interview. "I made records like Odelay because there was a certain sound and sensibility that I wanted to achieve, and it was eerie to find that they had already done it 30 years ago, in a totally shocking but beautiful and satisfying way.'

But what is merely a canny artistic strategy for today's artists, was a political necessity for Os Mutantes. Brazil was ruled by a military dictatorship when the group recorded, and all of its songs had to be submitted to government censors.