Rocksteady is a music genre that originated in Jamaica around 1966. A successor of ska and a precursor to reggae, rocksteady was performed by Jamaican vocal harmony groups such as The Gaylads, The Maytals, The Heptones andThe Paragons. The term rocksteady comes from a dance style that was mentioned in the Alton Ellis song “Rock Steady”. Dances performed to rocksteady were less energetic than the earlier ska dances. The first international rocksteady hit was “Hold Me Tight” (1968) by the American soul singer Johnny Nash; it reached number one in Canada.
halfway descent page on the rock and the steady at wikipedia