Be-bop, also known as bop, is a style of jazz characterized by complex chord progressions, intricate melodies, and fast tempos. There are several synonyms for be-bop that are commonly used in jazz circles. One of these is "hard bop," which emerged in the mid-1950s as a more aggressive and blues-influenced form of be-bop. Another synonym is "post-bop," which represents a more exploratory and experimental approach to be-bop that developed in the 1960s. Other related genres include cool jazz, modal jazz, free jazz, and fusion, all of which draw upon the improvisational and rhythmic traditions of be-bop while incorporating their own distinctive sounds and techniques.