The first popular jazz singer to move audiences with the intense, personal feeling of classic blues, Billie Holiday changed the art of American pop vocals forever. More than a half-century after her death, it's difficult to believe that prior to her emergence, jazz and pop singers were tied to the Tin Pan Alley tradition and rarely personalized their songs; only blues singers like Bessie Smith and Ma Rainey actually gave the impression they had lived through what they were singing.