Name one major contribution of Duke Ellington to jazz music.

Duke Ellington's major contribution to jazz music was his significant expansion of the big band format and the creation of sophisticated arrangements. He was a master composer and orchestrator, known for his ability to blend various musical influences and styles into his big band performances. Ellington's arrangements showcased intricate harmonies, innovative orchestration, and a deep understanding of the unique qualities of his musicians, allowing them to shine within the context of his compositions.

His work elevated the big band from merely a platform for dance music to an art form with a rich and expressive musical language. This transformation involved the careful crafting of pieces that included elements of improvisation, blues, and classical music, making his arrangements not only complex but also emotionally resonant. Ellington's compositions and arrangements, such as "Mood Indigo" and "Take the 'A' Train," are prime examples of his sophisticated approach and have had a lasting impact on the genre of jazz.

While the other choices reference significant developments or contributions in jazz, they do not accurately reflect Ellington's primary influence, which lies in his innovative arrangements and his role in advancing the art of big band jazz.