Emerging after World War II, R&B was a stripped-down, upbeat form that mixed jazz and blues over a back-shuffle snare beat, laying the foundation for rock 'n' roll. Raunchy lyrics continued an African-American tradition of setting sexual innuendos and double entendres to a danceable beat. Ray Charles & Little Willie John shared the limelight with female pioneers Ruth Brown & Big Mama Thornton. In the 1950s, R&B artists incorporated more pop-oriented time signatures and lyrical topics, moving the infectious sound into the popular mainstream.