It is from the blues that all that may be called American music derives its most distinctive characteristic.

Johnson is asserting that the blues—rooted in African American experience—functions as the foundational wellspring of what later listeners recognize as distinctly “American” in the nation’s popular and vernacular music. The claim is not merely genealogical (that later genres borrowed from blues), but aesthetic: blues supplies characteristic traits such as expressive “blue” notes, flexible rhythm, call-and-response phrasing, and a frank emotional directness that became central to jazz, gospel-inflected popular song, rhythm and blues, and rock. Implicitly, the quote also argues for cultural recognition: America’s musical identity is inseparable from Black creativity, and any account of American music that marginalizes the blues misunderstands its most defining features.