75 years ago an African-American singer named Marian Anderson stood on the steps of the Lincoln Memorial in Washington D.C and performed for tens of thousands of people. It's been called “The Concert that Shook the Establishment." During her lifetime - Anderson's unique voice was heard and praised around the world. She remains an important figure for music as well as civil rights. Ollie Watts Davis, a professor of voice at the University of Illinois at Urbana-Champaign is paying tribute to Anderson this weekend.