Hard-Bop is a musical style that involves the mixture of bebop and other styles, including but not limited to: blues, soul, latin and funk. It became prominent in the 1950's and continued to be popular throughout the 1960's. Some labels that are famous for hard-bop are Blue Note and Prestige. The classic instrumentation of a hard bop group consists of: a saxophone (alto or tenor), a trumpet, drums, upright bass and piano, although many artists did not always stick with this instrumentation. Guitar or organ could be added instead of or in addition to piano, trombone or flute could be added, or some of the staples could be taken out. Some notable artists include John Coltrane, Sonny Rollins, Clifford Brown, Lee Morgan, Dexter Gordon, and Wes Montgomery.