As we mark the 50th anniversary of the March on Washington, the anthem of the movement , We Shall Overcome, deserves a mention (link is to Wiki, with all the supposition of its origins).
Peter Seeger changed "We will" (the original) to "We shall" in 1947 and his version became the one circulated throughout the labor and civil rights movements.
"I changed it to 'We shall'... I think I liked a more open sound; 'We will' has alliteration to it, but 'We shall' opens the mouth wider; the 'i' in 'will' is not an easy vowel to sing well
Just before the march Pete performed at Carnegie Hall on June 8, 1963 and it included "We shall over come" with an introduction:
"If you would like to get out of a pessimistic mood yourself, I got one sure remedy for you. Go help those people down in Birmingham and Mississippi or Alabama. All kinds of jobs that need to be done. Takes hands and hearts and heads to do it, human beings to do it. And then we'll see this song come true."
As I have written many a times, I believe Pete Seeger is one of the greatest human beings of our times. His songs inspired (and continue to inspire) a generation of activists and singers, as did his courage in not giving in to the fear mongering of the 50s and 60s.
Testimony of Pete Seeger before the House Un-American Activities Committee, August 18, 1955.
Mr. SEEGER: I decline to discuss, under compulsion, where I have sung, and who has sung my songs, and who else has sung with me, and the people I have known. I love my country very dearly, and I greatly resent this implication that some of the places that I have sung and some of the people that I have known, and some of my opinions, whether they are religious or philosophical, or I might be a vegetarian, make me any less of an American. I will tell you about my songs, but I am not interested in telling you who wrote them, and I will tell you about my songs, and I am not interested in who listened to them. . . .
Source: Congress, House, Committee on Un-American Activities, Investigation of Communist Activities, New York Area (Entertainment): Hearings, 84th Congress, August 18, 1955
He was blackballed and charged with contempt of congress (something he and I have in common, although I was never charged ;-))
The music of the movement was an incredibly important part of energizing and comforting the people involved and spreading the message that "We shall overcome some day".