Singer-songwriter Sixto Rodriguez, referred to as "the greatest protest singer and songwriter that most people never heard of" in a 2013 Associated Press story, died Tuesday in Detroit. His albums flopped in the US in the 1970s, but he became a star in South Africa, inspiring white liberals horrified by the apartheid regime. His legacy would take off back home after the Oscar-winning documentary "Searching for Sugar Man" followed two South African fans who set out to discover what happened to their musical hero.