One of the few missing ingredients in the film Selma is the centrality of music during the Selma-to-Montgomery, Alabama march. A tiny snippet of field recordings from the march can be heard at the very end of the movie’s credits, but otherwise the movie ignores the constant singing that emboldened the marchers during the four-day, 54-mile trek.

Not surprisingly, Pete Seeger—who died almost exactly a year ago at age 94—was there to help lift the marchers’ spirits, as he did for every progressive crusade during his lifetime.

Rev. Martin Luther King invited Seeger to join the March 1965 protest that helped draw national attention to the horrors of Jim Crow segregation and the denial of voting right, and which led to the passage of the Voting Rights Act later that year. Other singers—including Odetta, Nina Simone, Joan Baez, Harry Belafonte, Leon Bibb, Ella Fitzgerald, and Peter, Paul and Mary—joined the march, too.

But the marchers didn’t need celebrities to get them to sing. Civil rights activists used songs—at church meetings, rallies, and protests, on buses during Freedom Rides, and even in jail—to boost their morale. They often revised Negro spirituals to fit specific occasions.

Seeger wasn’t at the march to entertain, but to help empower the protesters through their collective voice and to show his solidarity with the civil rights struggles. When the exhausted marchers stopped at night, pitching tents along the roadside, Seeger went from campfire to campfire, jotting down the words of their songs so he could spread their message. With Len Chandler and the Freedom Voices, Seeger compiled a collection of songs that were sung during the march or were inspired by that fateful protest, including “Do What the Spirits Say Do,” “Oh, Wallace,” “Which Side Are You On?” “Ain’t Gonna Let Nobody Turn Me ‘Round,” and “Keep Your Eyes on the Prize.” Folkways Records released the album, “WNEW’s Story of Selma,” a few months later.

Seeger played an important but little-known role in the civil rights movement. He and folksinger Guy Carawan had heard “We Shall Overcome” at the Highlander Folk School, a training center for civil rights and labor activists in Tennessee. They rewrote the words and music to make it more singable, then introduced it to activists at civil rights rallies and meetings. It soon became the movement’s anthem, but it didn’t stop there. Human rights activists around the world adopted “We Shall Overcome” as their own theme song. In that way, and in many other ways, Seeger brought the world closer together with his music.

Every day, every minute, someone in the world is singing a Pete Seeger song. For more than six decades, he introduced Americans to songs from other cultures, like “Wimowe” (“The Lion Sleeps Tonight”) from Africa, “Tzena, Tzena” from Israel (which reached #2 on the pop charts), and “Guantanemera” from Cuba, inspiring what is now called “world music.”

The songs he wrote, including the antiwar tunes “Where Have All the Flowers Gone?”, “If I Had a Hammer” and “Turn, Turn, Turn,” and those he popularized, including “This Land Is Your Land” and “We Shall Overcome,” have been recorded by hundreds of artists in many languages and have become global anthems for people fighting for freedom. His songs promote the basic idea that the hopes that unite us are greater than the fears that divide us.

Seeger was a much-acclaimed and innovative guitarist and banjoist, a globe-trotting minstrel and song collector, and the author of many songbooks and musical how-to manuals. He was on the front lines of every key progressive crusade during his lifetime—labor unions and migrant workers in the 1930s and 1940s, the banning of nuclear weapons and opposition to the Cold War in the 1950s, civil rights and the anti-Vietnam War movement in the 1960s, environmental responsibility and opposition to South African apartheid in the 1970s, and human rights throughout the world, always.

His remarkable spirit, energy, and optimism kept him going through triumphs and tragedies, but he outlived all his enemies.

The son of musicologists Charles and Ruth Seeger, Pete spent two years at Harvard, where he got involved in radical politics and helped start a student newspaper, the Harvard Progressive, but quit in 1938 to try changing society by making music. He worked at the Library of Congress’ Archive of American Folk Song (where he learned many of the songs he would sing throughout his career), traveled with Woody Guthrie singing at migrant labor camps and union halls and perfected his guitar- and banjo-playing skills.

In 1941, at age 22, Seeger formed the Almanac Singers with Lee Hays and Millard Lampell, later joined by Guthrie, Bess Lomax, and several others who rotated in and out of the group. The Almanacs drew on traditional songs and wrote their own songs to advance the cause of progressive groups, the Communist Party, the Congress of Industrial Organizations unions, the New Deal, and, later, the United States and its allies in the fight against fascism. The Almanacs were part of a broader upsurge of popular progressive culture during the New Deal, fostered by programs like the federal theater and writers’ projects. Even so, the group was hounded by the FBI, got few bookings, and was dropped by its agent, the William Morris Agency. After Seeger and Guthrie joined the military, the group disbanded in 1943.

The Almanacs cultivated an image of being unpolished amateurs. Guthrie once said that the Almanacs “rehearsed on stage.” Among them, however, Seeger was the most gifted and disciplined musician, with a remarkable repertoire of traditional songs. He carefully crafted a stage persona that inspired audiences to join him, a performing style that he perfected when he began working as a soloist. Every Seeger concert involved a lot of group singing.

In 1946 Seeger led the effort to create People’s Songs (an organization of progressive songwriters and performers) and People’s Artists (a booking agency to help the members get concert gigs and recording contracts). Seeger traveled with Henry Wallace during his 1948 campaign for president on the Progressive Party ticket, distributing song sheets at every meeting or rally so that sing-alongs could alternate with Wallace’s speeches.

For a brief period, as a member of the Weavers folk quartet, Seeger achieved commercial success, performing several chart-topping songs that reflected his eclectic repertoire. The group was formed in 1948 by Seeger and Hays (both former Almanacs), along with Ronnie Gilbert and Fred Hellerman. They exposed audiences to their repertoire of songs from around the world as well as to American folk traditions. Decca Records signed the Weavers to a recording contract and added orchestral arrangements and instruments to their music, a commercial expediency that rankled Seeger but delighted Hays. The Weavers performed in the nation’s most prestigious nightclubs and appeared on network television shows.

In 1950 their recording of an Israeli song, “Tzena Tzena,” reached number two on the pop charts, and their version of Lead Belly’s “Goodnight, Irene,” reached number one and stayed on the charts for half a year. Several of their recordings—”On Top of Old Smokey,” “Kisses Sweeter Than Wine,” the African song “Wimoweh,” and “Midnight Special”—also made the charts. Their 1951 recording of Guthrie’s song “So Long It’s Been Good to Know You,” reached number four.

But the Weavers’ commercial success was short-lived. As soon as they began to be widely noticed in 1950, they were targeted by both private and government witch-hunters. The FBI and Congress escalated their investigations. The Weavers survived for another year with bookings and even TV shows, but finally the escalating Red Scare caught up with them. Their contract for a summer television show was canceled. They could no longer get bookings in the top nightclubs. Radio stations stopped playing their songs, and their records stopped selling. They never had another major hit record.

Seeger left the Weavers to pursue a solo career, but he was blacklisted from the early 1950s through the mid-1960s. In 1955 he was convicted of contempt of Congress for refusing to discuss his political affiliations at a hearing called by the House Committee on Un-American Activities, although he never spent time in jail. (The conviction was overturned on appeal in May 1962). Many colleges and concert halls refused to book Seeger. He was kept off network television. In 1963 ABC refused to allow Seeger to appear on Hootenanny, which owed its existence to the folk music revival Seeger had helped inspire.

During the blacklist years, Seeger scratched out a living by giving guitar and banjo lessons and singing at the small number of summer camps, churches, high schools and colleges, and union halls that were courageous enough to invite the controversial balladeer. In 1966, on New York City’s nonprofit educational television station, he hosted a low-budget folk music program,Rainbow Quest, that gave exposure to many little-known country, bluegrass, and folk singers. The station had a limited viewership at the time, but fortunately the programs were taped and are now available on YouTube.

Eventually, however, Seeger’s audience grew. In the 1960s he sang with civil rights workers at rallies and churches throughout the South. In a letter to Seeger, Martin Luther King thanked him for his “moral support and Christian generosity.”

In 1967 Tom and Dick Smothers defiantly invited Seeger onto their popular CBS television variety show, the Smothers Brothers Comedy Hour. True to his principles, Seeger insisted on singing a controversial antiwar song, “Waist Deep in the Big Muddy.” CBS censors refused to air the song, but public outrage forced the network to relent and allow him to perform the song on the show a few months later.

Seeger helped catalyze the folk music revival of the 1960s, encouraging young performers, helping start the Newport Folk Festival, and promoting the folk song magazine Sing Out! that he had helped launch. His book How to Play the 5-String Banjo taught thousands of baby boomers how to play this largely forgotten instrument.

Many prominent musicians, including Bob Dylan, Bono, Joan Baez, the Byrds, Natalie Maines of the Dixie Chicks, Bonnie Raitt, Tom Morello, and Bruce Springsteen consider Seeger a role model and trace their musical roots to his influence. Many of his 80 albums—which include children’s songs, labor and protest songs, traditional American folk songs, international songs, and Christmas songs—have reached wide audiences. His travels around the world—collecting songs and performing in many languages—inspired today’s world music movement. Among performers around the globe, Seeger became a symbol of a principled artist deeply engaged in the world.

In 1969 Seeger launched the group Clearwater (near his home in Beacon, N.Y.) and an annual celebration dedicated to cleaning up the polluted Hudson River. The effort, at first written off as simplistic and naive, helped inspire the environmental movement. The Hudson, once filled with oil pollution, sewage and toxic chemicals, is now swimmable.

Through persistence and unrelenting optimism, Seeger endured and overcame the controversies triggered by his activism. In 1994, at age 75, he received the National Medal of Arts (the highest award given to artists and arts patrons by the U.S. government) as well as a Kennedy Center Honor, when President Bill Clinton called him “an inconvenient artist, who dared to sing things as he saw them.” In 1996 he was inducted into the Rock and Roll Hall of Fame because of his influence on so many rock performers. In 1997 he won the Grammy Award for his 18-track compilation album, Pete.

In 2012 Pete released two new albums. A More Perfect Union featured 16 original songs written with singer-songwriter Lorre Wyatt and includes duets with Springsteen, Morello, Earle, Harris, and Williams. The two-CD Pete Remembers Woody honored his friend as part of the centennial celebration of Guthrie’s birth.

In the year before he died, Seeger kept on singing for causes he believed in and even released a music video and an audiobook.

Probably no song reflects Pete’s indomitable spirit more than “Quite Early Morning,” the song he sang on the Colbert Report in 2012. The last verse goes:

So though it’s darkest before the dawn

These thoughts keep us moving on

Through all this world of joy and sorrow

We still can have singing tomorrows

Through all this world of joy and sorrow

We still can have singing tomorrows

Thanks to Pete, people around the world can have many “singing tomorrows.”

Peter Dreier teaches politics and chairs the Urban & Environmental Policy Department at Occidental College. His latest book is The 100 Greatest American of the 20th Century: A Social Justice Hall of Fame (Nation Books, 2012). Pete Seeger is one of the people profiled in the book.