Rhythm section (also called a backup band) is a group of musicians within an ensemble who provide the underlying rhythm and pulse of the accompaniment, providing a rhythmic reference for the rest of the band. Rhythm section comprises one or more guitars and/or a keyboard instrument and a double bass or electric bass, and drums. In some styles of music, there may be additional percussionists playing instruments such as the djembe or shakers. The guitars may be acoustic guitars, electric guitars, or a combination of both, depending on the style of music.