Developed by Negro musicians in New Orleans in the early 1900s and then popularized across the US by radio broadcasts and traveling musicians, jazz remains one of the principal musical genres more than a century later. Characterized by improvised melodic lines, substitute harmonies and syncopated rhythms. Sub-genres include swing, bebop, fusion, and smooth jazz, as well as styles tied to specific instrumentation such as big band jazz and boogie-woogie piano. Blues is a related style based on repeated 12-measure sections.