In contemporary jazz the term post-bop is used for artists and bands that apply original bop styles such as bebop and hard bop, but also free jazz, avant-garde and modal jazz, without tying themselves to a fixed genre. Rooted in jazz traditions in terms of rhythm, structure and improvisation techniques, but also progressive and sometimes with a view on pop, rock, classical or world music. Pioneers in this field include Miles Davis, John Coltrane, Charles Mingus and Wayne Shorter who started stretching jazz as early as the 1960s. They are also of great influence on contemporary post-bop artists.