The term itself, “swing,” has been used in a number of ways. Today, the most common use among jazz musicians relates to subtle changes in the timing of the melody, which promote a “swing feeling.” That is to say that the melody notes are played ahead of the beat, across the beat, or behind the beat, allowing the performer to express a more relaxed, rhythmic, or even driving feeling.
Another, more specific use of the term refers to the style of music played by big band dance orchestras of the 1930’s and 1940’s. But in the 1920’s, and before, musicians usually used the term “swing” as a synonym for “jazz.”
Regardless of the definition, there is little argument that Ellington’s “It Don’t Mean A Thing...” is the song that brought the word “swing” into general use. The song is further credited with predicting the swing era, giving the swing era its name, and providing one more reason to call Duke Ellington a prophet.