Over the course of her career the late singer Nina Simone left audiences with many different impressions -- from difficult to lovable to out and out hostile. But her contributions to music, and to the struggle for civil rights, are indisputable. On this Martin Luther King Jr. Day, we take a closer look an icon whose story is complex, and whose songs have become anthems. We take a look back at the voice behind songs like "Mississippi Goddam" with historian Ruth Feldstein, whose upcoming book is called How it Feels to be Free: Black Women Entertainers and the Civil Rights Movement.