Editor’s note: Yoruba Richen is the director and Mehret Mandefro and Lacey Schwartz Delgado are executive producers of American Masters: How It Feels to Be Free, a documentary that looks at the historical importance and overlooked contributions of Black performers. Focusing on Lena Horne, Abbey Lincoln, Nina Simone, Diahann Carroll, Cicely Tyson and Pam Grier, the docu — also executive produced by Alicia Keys — airs tonight on PBS in honor of Martin Luther King Jr.