From an interview with Pete Seeger - by Anita Krajnc and Michael Greenspoon - peacemagazine.org.
Pete Seeger, the consummate protest singer, has combined folk music and progressive politics since he began singing professionally in 1939 at the age of 20. He encouraged the whole audience to join in on variations of "Oh Freedom." Pete Seeger has helped popularize folk music in his travels across America with Woodie Guthrie in 1940, and with the Almanacs and then the Weavers in the '40s and '50s. Pete Seeger helped invent the "campus circuit" and through his travels across America, Seeger "taught most of America's younger folk performers.
In the 1950s, with postwar prosperity and the chill of McCarthyism and the Cold War, labor turned inward, away from radicalism and the picket lines. He helped adapt and popularize "We Shall Overcome." The song became the anthem of the civil rights movement.
Protest music has often played a significant role in social change movements. The labor and civil rights movements were great singing movements. Protest music has served to draw in new participants into movements and strengthen the commitment of existing members.