After marrying alto and baritone saxophonist John Williams in 1927, she would regularly sit in with his Memphis-based band The Syncopators. When John moved to Oklahoma City, Mary Lou stayed in Memphis, taking over leadership of the band, which occasionally featured the future great, Jimmy Lunceford. In 1929, she moved to Kansas City to join Andy Kirk’s band. In addition to her musical contributions, she would also handle a variety of other responsibilities, from driving the band’s bus to sewing clothes.

By 1931, she’d become the band’s official pianist and chief arranger and would remain so until 1941. During those same years, Mary Lou also arranged for Duke Ellington and Benny Goodman, along with many other Swing era bands, including Louis Armstrong, Earl Hines, Cab Calloway and the Dorsey Brothers.

Upon leaving Kirk, she formed her own band which included Art Blakey and her second husband, trumpeter Harold "Shorty" Baker. Parts of her 1945 12-part Zodiac Suite were scored for the New York Philharmonic one year later and Mary Lou was featured on piano for its Carnegie Hall performance. She was quickly becoming one of the most respected Jazz composers, writing over 350 compositions during her 50+ years in Jazz.

Throughout all the various circumstances of her career, Mary Lou was always viewed as a modernist. Transcending gender barriers, she was not only a pioneering inspiration to future women artists, but to many of the major proponents of the Bebop era. Charlie Parker, Thelonious Monk, Miles Davis, Tadd Dameron, Bud Powell were just some of the greats who made Mary Lou’s New York residence their central office.

A headliner on the club and concert circuits in both the U.S. and Europe, she moved abroad in the early ‘50s and returned to New York in 1955, dropping out of the music scene to immerse herself in Catholicism and focus on composing Sacred music, which remained a primary interest for the rest of her life. Returning to peforming in the ‘60s, she founded the Pittsburgh Jazz Festival in 1964, serving as its director for three years.

By the 1970s, Mary Lou began to receive the honors that her pioneering efforts as both musician and activist entitled her. Recognition of her contribution to the world of music came in the form of honorary degrees from Fordham, Boston and Loyola Universities and Manhattan, Bates and Rockhurst colleges, as well as two Guggenheim Fellowships. In 1973 a street was named in her honor in Kansas City. She was the featured performer at the International Premiere Concert of the Women’s Jazz Festival in March 1978. In the same year, she was a featured performer at President Jimmy Carter’s White House Jazz Party. She founded and served as President of the Bel Canto Foundation for needy musicians as well as the general poor and young children, and she started the New Reform Foundation for gifted children between the ages of 6 and 12. She conducted musical workshops in storefronts and on the streets of Harlem.

One of the few artists who successfully made the transitions through every change that confronted the Jazz form, her late ‘70s duets with avant-garde piano giant Cecil Taylor proved her continued innovative and adventurous vision. From 1977 until her death in 1981, she was artist-in-residence at Duke University.

No higher tribute can be made than that of the one and only Duke Ellington who once proclaimed: