Rocksteady was a style of popular music that developed out of ska in the 1960s. In its simplest terms, rocksteady is half-speed ska with the trombone replaced by piano and prominent bass. The lyrics are more socially and politically conscious, and there is a greater focus on harmonies, particularly in trios like the Heptones, Gaylads, Dominoes, Aces, and Wailers. Other major figures include Alton Ellis and Ken Boothe. With its relaxed beat and social-protest lyrics, the music served as a forerunner to reggae.