Time and again, we've seen aging stars trying -- and failing -- to regain the vibrant playfulness of youth. So how has original Mutant, 57-year-old Sergio Dias (who came through the chemical-infused cauldron of '70s-era Brazil), retained it? No matter. He has, and transmitted it to the next-generation Os Mutantes, gently guiding them away from the musically obvious and toward the strange. The high drama of prog, the persistent randomness of psychedelia, samba's joy ... it's all here, but what enchants is that relentless impulse to meddle. Os Mutantes are dead; long live Os Mutantes!