The first significant female composer and pianist in jazz, Mary Lou Williams was a child prodigy, who worked in and around Pittsburgh as Mary Lou Burley. In 1925, she went on the road with a revue, and the following year ended up marrying the show's bandleader and saxophonist John 'Bearcat' Williams. Their careers were inextricably intertwined in a series of show and territory bands, and then in the Clouds of Joy, led by Andy Kirk, for whom Mary Lou became arranger and pianist.
Her charts were novel, exciting and hard-swinging, with the professional edge of the born composer, and her playing added zest to what was sometimes a rather stodgy rhythm section. She left Kirk in the early 1940s, leading a band with her new husband, trumpeter Shorty Baker. When he joined Duke Ellington, Mary Lou ended up writing and arranging for Duke's band, but before long was leading her own groups at Cafe Society in New York.
She became something of a fixture there, and as well as working with a broad cross section of players from swing era giants like Benny Goodman to bebop pioneers such as Kenny Clarke, she made many discs of her own. In the 1950s she moved to Europe and briefly abandoned music as a career, but she returned to playing before the decade was out. During the 1960s and 70s she toured frequently, taught at various universities, and remained a regular participant in New York's jazz scene. She also wrote large scale orchestral works including her Zodiac suite and a Mass.