In his book Hard Bop: Jazz and Black Music 1955-1965, David Rosenthal outlines a group of musicians within the hard bop idiom that he identifies as “experimentalists”, describing them as “…consciously trying to expand jazz’s structural and technical boundaries: for instance, pianist Andrew Hill, Sonny Rollins, and John Coltrane prior to his 1965 record Ascension. This category would also include Thelonious Monk and Charles Mingus, whose playing and compositions were at once experimental and reminiscent of the moods and forms of earlier black music, including jazz of the 1920s and 1930s. Mingus, for example, composed and recorded ‘My Jelly Roll Soul,’ which is simultaneously a tribute to Jelly Roll Morton and a successful attempt to transmute and reformulate Morton’s compositional style in modern jazz terms… These musicians, by influencing and challenging [the other hard bop musicians], kept hard bop from stagnation. Even at their most volcanic, their performances were pervaded by a sense of thoughtful searching.”