Music played a key role in the freedom movement. And the great Mavis Staples and her family were right in the thick of it.
Linked here is a clip of Mavis talking about the first time she saw Dr. King in person (the second clip in the box below "Meeting MLK"):
Here's a tremendous live recording of "Why Am I Treated So Bad", the song that Mavis says was Dr. King's favorite. In addition to everything else the great man accomplished, looks like he had good taste in music as well:
Mavis Staples web page: http://www.mavisstaples.com/