How a run-down Ford launched a music revolution that swept Brazil’s Carnival

Sound begins blasting ear drums and rattling bones even before the speakers — hauled by big rigs creeping their way through Brazil’s thronging Carnival crowds — draw near.

The behemoth sound trucks known as electric trios are a Brazilian innovation that amplified music and effectively did away with front-row seats — making Carnival more accessible. In the seven decades since the first one hit Brazil's streets, they have become a fixture of the country's annual pre-Lenten festivities and draw millions to the streets. Singer Caetano Veloso's ode to the earth-shaking vehicles proclaimed that the only people not following them must already be dead.

From , on Brazil's northeast coast, trios spread throughout the