For every history-making moment of the American Civil Rights Movement, there was an accompanying song. Protesters sang about sitting in, about marching, about deposing George Wallace, all before actually doing it, and spirituals that may have otherwise been forgotten were revived. Most fascinating, activists would often improvise new lyrics to the traditional melodies to maintain morale while the police brutalized marchers and sprayed firehoses at children. Soundtrack to a Revolution pulls together newsreel footage alongside new interviews with leaders from the era. The film’s rich supply of period footage could stand on its own, but new performances by John Legend, the Blind Boys of Alabama, the Roots (with members of TV on the Radio), Joss Stone, Wyclef Jean, and several other musicians add perspective and depth.