On the first Saturday of Jazz Fest 2013, Charles Bradley strode out on the Blues Tent stage as if he weren’t 65 years old but as if it were 1973 and he were 25 with his whole career ahead of him. He wore a bright purple jumpsuit unzipped to the waist and a rounded afro the size of a soccer ball. When he started singing “In You (I Found a Love)” from his debut album, the trumpet and tenor sax punched out a tight R&...