John Aaron Lewis (3 May 1920 – 29 March 2001) was an American jazz pianist and composer best known as the musical director of the Modern Jazz Quartet.
Born in LaGrange, Illinois and raised in Albuquerque, New Mexico, he learned classical music and piano from his mother starting at the age of seven. He continued his musical training at the University of New Mexico and also studied anthropology. He served in the Army in World War II. While stationed in France on a three-year tour of duty, he met and performed with Kenny Clarke. Clarke was an early developer of the bop style and Lewis composed and arranged for a band he and Clarke organized. Lewis returned from service in 1945 and resumed his university studies.
In the fall however, he went to New York where he found work in 52nd Street clubs with Allen Eager, Hot Lips Page and others. After that year, he joined Dizzy Gillespie's bop-style big band where Clarke was the drummer. Lewis developed his skill further by composing and arranging for the band as well as attending the Manhattan School of Music. In January 1948, the band made a concert tour of Europe, interrupting Lewis' studies. Lewis stayed in Europe for a time after the tour, writing and studying piano. He returned to the United States and started working for Charlie Parker in 1948 (he recorded the piano part on the famous recording "Parker's Mood"), Illinois Jacquet from October 1948 to 1949, Lester Young from 1950 to 1951, and others. He participated in the second Birth of the Cool session with Miles Davis in 1949 but was unable to attend the first because of an engagement with Ella Fitzgerald, whom he accompanied. Al Haig substituted for him, and the band did not include a pianist for its third session in 1950. Lewis arranged the compositions "Move" and "Budo" (immediately released as singles in 1949) and contributed one tune, "Rouge," to these seminal sessions.