Jazz music is messy; the trends are complex and often go back and forth in surprising ways.
As a historian of jazz, it's tempting to buy into this model of the music progressing in an eternal Hegelian motion towards progress and greater and greater things. It's an easy way to write a book on the history of music, to say, "Each generation takes what the previous generation did and pushes it two steps forward." But that narrative doesn't do justice to the real life activities of jazz musicians. Jazz music is messy; the trends are complex and often go back and forth in surprising ways. Even in the midst of writing a history of jazz, I wanted to make sure people knew that fitting this thing into a historical progression could mislead them.