Three years after sports comes the earliest reference we have to “jazz” as music:

“Blues Is Jazz and Jazz Is Blues . . . The Worm had turned – turned to fox trotting. And the "blues" had done it. The "jazz" had put pep into the legs that had scrambled too long for the 5:15. . . . At the next place a young woman was keeping "Der Wacht Am Rhein" and "Tipperary Mary" apart when the interrogator entered. "What are the blues?" he asked gently. "Jazz!" The young woman's voice rose high to drown the piano. . . . The blues are never written into music, but are interpolated by the piano player or other players. They aren't new. They are just reborn into popularity. They started in the south half a century ago and are the interpolations of darkies originally. The trade name for them is "jazz." . . . Thereupon "Jazz" Marion sat down and showed the bluest streak of blues ever heard beneath the blue. Or, if you like this better: "Blue" Marion sat down and jazzed the jazziest streak of jazz ever. Saxophone players since the advent of the "jazz blues" have taken to wearing "jazz collars," neat decollate things that give the throat and windpipe full play, so that the notes that issue from the tubes may not suffer for want of blues – those wonderful blues.”
[Seagrove, Gordon, Chicago Tribune, 11 July 1915. Jazz (word) wiki copypasta]

Note how the 1915 author uses the blues and jazz genre labels indiscriminately, as hokum is/was defined:

“...In the days before ragtime, jazz and even hillbilly music and the blues were clearly identified as specific genres, hokum was a component of all-around performing, entertainment that seamlessly mixed monologues, dialogues, dances, music, and humor.” [Hokum wiki]