The reason jazz started in New Orleans is because it was supported economically there by
the whorehouse industry. Also the marching band was employed for municipal functions.

After the Navy closed down Storyville, jazz moved to Chicago and ultimately to the other big cities.

Jazz (jass) is also a euphemism (like rock) that would be applied to the red light district of
Storyville.

(Jazz is an acceptable four-letter word).