In the 1950s, Holman worked with her accompanist, Gerald Cook, on researching and rearranging what they called earth music. It was primarily blues and spirituals that were linked to the African American community. She was involved in the Civil rights movement and became a close friend and associate of Martin Luther King Jr. Through her foundation she provided funds for King's trip to India with his wife, Coretta Scott King, to meet followers of Mahatma Gandhi, whom he referred to as "the guiding light of our technique of nonviolent social change".