Os Mutantes were formed in São Paulo, Brazil, in 1966 by brothers Arnaldo Baptista and Sérgio Dias and lead singer Rita Lee. Active during the Tropicalia movement of the late 1960s, they took Brazilian music and fused it with British rock and American psychedelia to create a distinctive, vibrant sound. Along with Gilberto Gil, Caetano Veloso and Tom Zé, they helped define the Tropicália movement.