An expressive style of music can refer to two distinct genres: Ska and RAP. Ska is a genre of music that originated in Jamaica in the late 1950s, combining elements of Caribbean mento and calypso with American jazz and rhythm and blues. It is characterized by a walking bass line, guitar and piano accents, and a drum pattern known as the skank. RAP is a genre of popular music that originated in the United States in the mid-1970s. It is characterized by rhyming lyrics spoken over a beat or instrumental track. RAP is often used to express social and political issues, and it has become one of the most popular forms of music in the world.