Ben Johnston (b. 1926) is an American composer known for his contributions to contemporary classical music, particularly in the realm of microtonality. His work often incorporates just intonation, a system of tuning that contrasts with the equal temperament commonly used in Western music. Johnston studied under notable figures such as Henry Cowell and Darius Milhaud, and he was influenced by the music of the American avant-garde. Notable works include his string quartets, especially the "String Quartet No. 4," which explores microtonal tuning, and "The Fourth Quartet," which is praised for its innovative use of pitch and rhythm. Johnston also composed music for various ensembles, including vocal works and pieces for solo instruments. His impact on music lies in his pioneering exploration of microtonal harmony and the integration of mathematical concepts into musical form. Johnston's work has influenced a generation of composers interested in expanding the boundaries of tonality and has contributed to the broader discourse on alternative tuning systems in contemporary music. His legacy continues to inspire musicians and scholars in the fields of microtonal and experimental music.