Pete Seeger performing in a scene from the movie “Pete Seeger: The Power of Song.”

I was 16 years old when I first heard Pete Seeger at a concert in Detroit. His message of peace, freedom, and human rights seemed to pierce the clouds that hung over our country in the dark days of McCarthyism.

I was so taken with Pete and his music that I successfully lobbied my high school student council to invite him to sing at one of our monthly assemblies.

He came for an hour, and led 600 students through “Wimoweh,” “This Land Is Your Land,” “So Long, It’s Been Good To Know You,” and other songs. They loved him.

The next day, two government agents showed up at the school. A friendly teacher told me that they had interviewed our principal, wanting to know the “words to the songs that Mr. Seeger had sung.”

That story came back to me while watching the movie “Pete Seeger: The Power of Song,” which was recently broadcast on PBS and can be seen for free at www.PBS.org. For 90 minutes the film glides through Pete’s life, from his childhood to his days as a union singer with Woody Guthrie, from the music he brought to the civil rights movement to his vision for cleaning up the Hudson River.

His words comforted and energized many, but their message of peace and justice also alarmed others.

In the 1950’s, conservatives picketed his concerts, and the House Un-American Activities Committee charged him with contempt of Congress because they didn’t like how he answered their questions.

As a result, Pete and his top-of-the-charts group the Weavers were blacklisted, and Pete was barred from commercial TV for 17 years.

He made a living by giving banjo lessons and singing before students like those at my high school – which paid him all of $60 for his performance.

Pete always knew he would overcome those dark times. Today he is acclaimed as one of America’s heroes.

Near the end of the movie, we see President Bill Clinton bestowing the Kennedy Center award on him, as Roger McGuinn leads the audience in one of Pete’s songs, “Turn, Turn, Turn,” reminding us that “to everything there is a season.” Even former New York Governor George Pataki is shown acknowledging Pete’s success in cleaning up the Hudson.

Bruce Springsteen, Joan Baez, the Dixie Chicks’ Natalie Maines, Arlo Guthrie, Bob Dylan, and many others pay tribute in “The Power of Song” to Pete’s influence on music and society.

(Indeed, at my 50th high-school reunion, a classmate whom I hadn’t seen since graduation stopped to thank me for introducing him to Pete’s music back at that school assembly.)

But the highlight of the movie is watching Pete himself sing through the years on picket lines, in concert halls, in classrooms, and elsewhere – never giving up in his core belief that the power of song can help us feel better about ourselves and our planet. When even members of a movie audience start to sing along, you know he’s right.

I felt Pete’s energy and dedication several times in recent years. He was a surprise guest at a party when I retired as editor of the UAW magazine Solidarity.

After a concert at Symphony Space in New York a couple of years ago, Pete led several hundred of us on a two-mile late-night march down Broadway to Columbus Circle as part of the Occupy movement in which many Local 802 members participated. At about the same time, Local 802 bestowed him with a lifetime achievement award during the union’s 90th birthday celebration.

Just two months ago, he showed up with fellow artist Harry Belafonte at a reception for The New Press at the Housing Works bookshop in SoHo. Ever optimistic, Pete, at 94, talked about the ability of music to change society, and then hoisted his banjo over his shoulder and led the bookstore crowd in song.

Pete leaves us a book of songs that he helped popularize, “Carry It On.” There couldn’t be a more enduring message than that from a man who never doubted that future generations would continue to harness the power of song to help change the world.

This essay, recently updated, originally appeared in Allegro in 2007. The author is the retired editor of Solidarity magazine, published by the United Auto Workers.