It's nothing short of miraculous that American audiences are getting the chance to see Os Mutantes. The legendary Brazilian group never played an American show in their heyday; indeed, most Americans had never heard of them until years after the Tropicália movement had come and gone. But over the years it became clear that Os Mutantes were one of the greatest rock bands that ever existed, and in 2006, founding members (and brothers) Sérgio Dias Baptista and Arnaldo Baptista reconstituted the group for a handful of shows. Now Sérgio has teamed with legendary Brazilian songwriter (and fellow Tropicálista) Tom Zé to compose Haih or Amortecedor, the first new Os Mutantes album in 35 years.

It's a willfully weird album, and one wouldn't expect anything less from Os Mutantes. But the youthful, wide-eyed psychedelia of the group's classic work has given way to a wiser—if not older—outlook. In some ways, Haih or Amortecedor is more fiercely subversive than anything the group has ever done, with Western musical styles inverted and traditional Brazilian sounds exposed to their core.

A lot of this has to do with collaborating with Zé in the songwriting, says Sérgio. "We met 40 years ago and I was too young to talk to him then. We started together but then we had totally separate lives, and then we got together now and he became the best partner I've ever had in terms of writing music."

The Tropicália movement was an artistic and political one; under Brazil's military dictatorship in the late '60s, artists and musicians celebrated the absurdist and exploratory qualities of the counterculture movement happening at that time in Western society, injecting it with a fierce Brazilian identity. The movement was soon squelched by Brazil's oppressive government, but Os Mutantes continued; Arnaldo and fellow Mutante Rita Lee Jones were married in 1971, but divorced a year later, and Jones left the group to go on to a hugely successful solo career. Arnaldo left shortly after, and Sérgio carried on with Os Mutantes until 1978.

The acid-dipped optimism of their music had a dark side, and in 1982 Arnaldo jumped out a window on ex-wife Jones' birthday. Having survived the leap, Arnaldo participated in the reunion shows in 2006 and 2007, but has since had to bow out from Os Mutantes. "I think the thing was too hard on him," says Sérgio. "He's not as strong as he was, especially after the so-called accident. It's not something I can make a choice [about] because his wife has the guard of his ability to be able to say yes or no to anything."

Meanwhile, Arnaldo's ex-wife Jones had some unkind words to say about the reunion, saying it was to "earn cash to pay for geriatry."

"Well, it was a sad thing for her to say," says Sérgio. "Rita obviously is as crazy as him, and I think Mutantes was always kind of a shadow on her career. They were sweethearts and they lost, like, their cherries to each other, and when we came back, I think he haunted her somehow."

Old grudges aside, the return of Os Mutantes is a very welcome thing, and the playful humor of their music is all the more vital. "Life is so serious, man," says Sérgio. "I think it's very easy to become cynical and bitter with the hardships of life. So if you don't have a laugh over it, you know, it becomes too heavy."