Forty-two years ago this month, a group of tobacco workers in Charleston, S.C., were in the midst of a bitter six-month strike against the American Tobacco Co. The union pickets, many of them black women, kept up their courage by singing.

Their favorite song was a traditional hymn called "I'll Be All Right." Walking the line, the pickets changed one line, "I will overcome," to "We will overcome."

Eleven years later, folk singer Pete Seeger sang the song, somewhat changed in lyrics and melody and now titled "We Shall Overcome," to the Rev. Martin Luther King Jr.

Afterward, according to Seeger, King told a friend: "You know that song, it really sticks with you."

As was so often the case, King's words proved prophetic. On a warm August day in 1963, more than 200,000 marchers who had gathered at the Lincoln Memorial to hear King's "I Have a Dream" speech linked arms and joined voices to sing the song. Two years later, newspapers reported that civil rights worker Viola Gregg Liuzzo sang "We Shall Overcome" as she lay dying of gunshot wounds. About that time, President Lyndon Johnson made note of the song in a nationally televised address on civil rights. And that same year, the song echoed through a Johannesburg prison when John Harris, a white South African sentenced to death for planting a bomb in protest against apartheid, sang it as he was led to the gallows.

The song that wended its way from the oral tradition of black spirituals to the labor movement of the 1940s had become the anthem of the civil rights movement, a song that filled the air at rallies, marches, sit-ins, boycotts, jailings and even beatings, lending courage to those who worked to bring a new order. As Vernon Jordan put it, "The people were cold with fear, until music did what prayer and speeches could not do in breaking the ice."

Today, that song is sung around the world.

Students in Seoul sang it in Korean when they took to the streets last fall. Seeger led a Japanese audience in an English rendition at Hiroshima in 1986. And last August, in the West African country of Togo, when Bishop Desmond Tutu, the South African Nobel laureate, was elected president of the All Africa Churches organization, "the whole place erupted and we sang that song," Tutu remembered.

What accounts for the emotional impact of the song?

"It's the genius of simplicity," says Seeger, who is credited with changing "will" to "shall" in the song's chorus and adding the verse "We'll walk hand in hand." "Any damn fool can get complicated. I like to compare it to the backboard in basketball. You bounce your life experiences off it and they come back with new meaning."

Bernice Reagon, who documented the history and evolution of "We Shall Overcome" in her doctoral dissertation at Howard University, writes that the song gave "added strength in crisis situations" of the civil rights movement.

It is Reagon, director of the program in black American culture at the National Museum of American History, who traces the song's origin to the black hymn "I'll Be All Right," whose lyrics, she writes, "point to a belief in a day or period when present conditions would change."

"I'll Be All Right" was a popular hymn in black Baptist and Methodist churches at the turn of the century. By the time of the American Tobacco strike, the song was being called "I Will Overcome" in some parts of the country, according to Reagon.

The strike, an arduous chapter in the lives of American Tobacco workers, began in October 1945 when the CIO-affiliated Food, Tobacco and Agricultural and Allied Workers Union walked out in Charleston. Accompanied by a national boycott of American Tobacco products, it lasted until April 1946, when it ended with concessions to the strikers, Reagon writes.

Years later, some of the striking workers told her that "I Will Overcome" was essential in maintaining the workers' determination. It was they who began singing "We" instead of "I."

In 1947, some of the Charleston strikers participated in a workshop at the Highlander Folk School in Monteagle, Tenn. The school's music director, Zilphia Horton, learned "We Will Overcome" from them, taught it to her students and published it in the center's songbooks, which were sent to labor organizers.

Seeger learned the song from Horton that year. "She taught it to me," he says. "But I still didn't get the rhythm right with my banjo." Because of Seeger, writes Reagon, by the mid-'50s the song was a standard at "progressive gatherings in New York and on the West Coast."

But it is folk singer Guy Carawan, who took Horton's job at Highlander after her death in 1957, who is credited with bringing the song into the Southern civil rights movement in the early 1960s. As Highlander's music director, he was asked to provide the music at rallies and other gatherings. Says Seeger: "Carawan taught it to SNCC {Student Nonviolent Coordinating Committee} people. They put the soul beat on it."

In 1963 "We Shall Overcome" in its present version was copyrighted for the first time under the names of four people, all of them white: Seeger, Carawan, Horton and Frank Hamilton, a folk singer who taught the song to Carawan in 1953. All royalties go to a Highlander fund for black songwriters and composers.

But even though no recordings or sheet music of the song existed before its copyrighting, it had spread far and wide. Many people heard it for the first time in concerts by the "Freedom Singers," a group of black civil rights supporters.

According to Seeger, PBS is preparing a documentary on the song's history for airing next year. It is a history that takes in much of the civil rights movement in America. What is harder to trace is the meaning that the song has held for the millions who have sung it. As Reagon puts it:

"It's a song, but it's also a way {of saying} you've changed your position in the world. I think that's where the power comes from. You're announcing you've changed."