An evolution of bebop. Emerged in the mid-1950s and its origins are most closely associated with the Jazz Messengers, a quartet led by Art Blakey on drums and Horace Silver on piano. Influenced by R&B, gospel and blues - most notably in the piano and saxophone playing - hard bop is often associated with soul jazz because of its stylistic characteristics. Some critics describe hard bop as a direct response to the relaxed style of cool jazz or west coast jazz, created by a generation of musicians who were raised during a time when bebop and R&B were the most prevalent genres of African-American music. Prominent hard bop musicians included Horace Silver, Charles Mingus, Art Blakey, Cannonball Adderley, Miles Davis, and Thelonious Monk.