Pete Seeger's life, like the arc of the moral universe famously invoked by Dr Martin Luther King Jr, bent toward justice. He died this week at 94. Pete sang truth to power through the epic struggles of most of the last century, for social justice, for civil rights, for workers, for the environment and for peace. His songs, his wise words, his legacy will resonate for generations.

Pete's parents were musicians. They traveled the US, exposing their children to the music of rural America. By 19, Pete was working for the acclaimed folklorist Alan Lomax, recording and cataloging folk songs for the Library of Congress. There he met Woody Guthrie, the legendary Depression-era troubadour of the working class, who was just a few years older. Seeger traveled with Guthrie, learned to hop freight trains and became inspired to unite his passion for the pursuit of justice with his musical talent. He, Woody and others formed the Almanac Singers in 1940. They lived communally in New York's Greenwich Village, and eked out a living by performing. Then came the second world war.

Pete was drafted into the army. When I asked him in 2004 about his military service, he recalled:

﻿"I first wanted to be a mechanic in the air force. … But then military intelligence got interested in my politics. My outfit went on to glory and death, and I stayed there in Keesler Field, Mississippi, picking up cigarette butts for six months."

He was later transferred to Saipan, in the Pacific, organizing entertainment for troops recuperating in the military hospital there. While on furlough in New York City, Pete proposed marriage to his sweetheart, Toshi Ohta. Toshi died last year at 91, just months shy of their 70th wedding anniversary.

After the war, Pete and three others formed a folk group called The Weavers. They became a national sensation. Then, Senator Joseph McCarthy's witch hunt against suspected communists blacklisted The Weavers off the radio. Seeger testified before the House Un-American Activities Committee (HUAC) on 18 August, 1955. He took a principled stand, politely admonishing his interrogators:

"I am not going to answer any questions as to my association, my philosophical or religious beliefs or my political beliefs, or how I voted in any election, or any of these private affairs. I think these are very improper questions for any American to be asked, especially under such compulsion as this."

He was charged with contempt of Congress, found guilty at trial and sentenced to a year in prison. Though his conviction would later be overturned, his biographer, David King Dunaway, in the PBS documentary Pete Seeger: The Power of Song, described the FBI's ongoing harassment of Seeger:

﻿ "The FBI basically pursued Pete Seeger to the point where he couldn't get a job. The only people that he could sing for were kids, because they never thought there'd be a problem with Pete Seeger singing for six-year-olds. Little did they know. Out of that came, not a subversive movement, but instead, an American folk-music revival that I think we have to give the FBI credit for helping to establish."

Pete met another target of FBI surveillance and intimidation, Dr Martin Luther King, at the Highlander Folk School in Tennessee in 1957. Seeger helped King and other civil rights activists incorporate song into their organizing tactics. It was at Highlander that Seeger first sang for King what would become the anthem of the civil-rights movement, We Shall Overcome

Like King, Seeger became an increasingly vocal critic of the US war in Vietnam. He finally overcame the McCarthy-era blacklist with an appearance on the hit TV show The Smothers Brothers Comedy Hour in 1967. Nevertheless, one of his songs, Waist Deep in the Big Muddy, was censored by CBS. The song allegorically described Vietnam as a quagmire, depicting President Lyndon B Johnson as "the big fool" who "says to push on". His performance of that song eventually aired on the show, months later, after a storm of protest against the network.

Pete Seeger continued singing, for peace, nuclear disarmament and, most notably, the environment. He founded the nonprofit Hudson River Sloop Clearwater. He and others built a sailing vessel, the Clearwater, and used it to educate and champion the cleanup of the Hudson River, which his home overlooked. "Now the Hudson is clean enough to swim in," Pete told me when I interviewed him in August of last year. When I asked him to sing We Shall Overcome, he did, saying: "Yes, that is something the human race needs to be reminded of. Don't give up."

Back in 1955, at the HUAC hearing, he was asked what he did upon returning from the war. He replied, "I continued singing, and I expect I always will." And so he did, changing us all.

• Denis Moynihan contributed research to this column.

© 2013 Amy Goodman; distributed by King Features Syndicate