Many regard Duke Ellington as the most important figure to emerge from the U.S. jazz scene in the twentieth century, although Ellington himself might have quibbled with the description, as he was reluctant to describe his work as anything more specific than "music". The word "jazz" was too narrow for Ellington, a man whose greatest compliment was to describe others who had impressed him as "beyond category". Indeed, Ellington has proved to be enigmatic, slipping through the easy classifications of biographers. Musicians run into much the same kind of problem when dealing with Ellington's compositions. Musically, he wore many hats, and he could never settle on just one. Through the ranks of Duke Ellington's Orchestra passed some of the biggest names in jazz. They included Johnny Hodges, Cootie Williams, Bubber Miley, Joe "Tricky Sam" Nanton, Barney Bigard, Ben Webster, Harry Carney, Sonny Greer, Otto Hardwick, Clark Terry, Jimmy Blanton, Ray Nance, Paul Gonsalves, and Wellman Braud.

Many of these musicians played in Ellington's orchestra for decades, and while most were noteworthy in their own right, it was Ellington's musical genius that melded them into one of the most well-known orchestral units in the history of jazz. Music critics agree that Ellington's ability to write and arrange for personalities rather than instruments made every section of his arrangements breathe with character. Ellington and his band (in its various incarnations) were prolific.