Pete Seeger performs with his grandson Tao, left, and Bruce Spingsteen during the We Are One: Opening Inaugural Celebration at the Lincoln Memorial in Washington on Jan. 18, 2009. (Alex Brandon/Associated Press)Folk music legend Pete Seeger is being honoured with a sold-out concert in New York's Madison Square Garden, marking his 90th birthday.

A parade of 30 music stars — including Bruce Springsteen, Arlo Guthrie, Steve Earle, Billy Bragg, Kris Kristofferson and Joan Baez — are taking part in the four-hour serenade on Sunday night. Canadians Bruce Cockburn, Martha Wainwright and Kate and Anna McGarrigle are also on the bill.

Proceeds from the show will go to Hudson River Sloop Clearwater, an organization founded by the singer 40 year ago to preserve and protect the Hudson River. Seeger now lives in the Hudson Valley area of New York state.

At age 90, Seeger is still planning performances throughout the year, performing last month in April in New Orleans. His most recent release, At 89, won a Grammy in February for best traditional folk album.

Once a card-carrying Communist and still an ardent social activist, Seeger has gone from pariah of the U.S. government to left-wing icon.

Quits Harvard, meets Woody Guthrie

Seeger was born May 3, 1919, in New York City to a middle-class family.

He dropped out of Harvard in 1938 and began wandering the country. After meeting folk musician Woody Guthrie in 1940, they formed the Almanac Singers, who became known for their pro-union protest songs.This 1959 photo shows Pete Seeger performing at the Highlander Research and Education Center in Monteagle, Tenn., once the headquarters for the struggle for the U.S. civil rights movement. (Tennessee State Archives/Associated Press)

Around 1948, Seeger formed his own group, the Weavers, which had several hits.

Some of the iconic songs that he has collaborated on or adapted include Turn Turn Turn, If I Had a Hammer, Where Have All the Flowers Gone? and We Shall Overcome, which became the civil rights anthem.

During the 1950s, Seeger was blacklisted for his former membership with the Communist Party. In 1955, he fought with the House Un-American Activities Committee, which had been on a witch-hunt for Communists.

Seeger was indicted for contempt of Congress two years after appearing before the committee.

After some legal wrangling, he was convicted in 1961 and sentenced to a year in prison.

His lawyer managed to get him off the charge on appeal that year. But Seeger's blacklisting already had a desired result — he wasn't shown on television between 1950 and 1967.

Still looking ahead

Seeger remains unrepentant and positive about his past.

"America's treated other people much, much worse… let's look ahead!" Seeger told BBC News in a recent interview.

During the 1990s, his reputation got a revival of sorts. He received a Kennedy Center honour and was also inducted into the Rock and Roll Hall of Fame.

He remains in the spotlight mostly due to Springsteen, who introduced a younger generation to the folk artist through the 2006 album, The Seeger Sessions.

Springsteen was also the catalyst for bringing Seeger to perform with him at the pre-inauguration concert in Washington, D.C., for U.S. president-elect Barack Obama back in January. He sang Woody Guthrie's This Land is Your Land.

Seeger, ever the activist, is not content to fade away. He still has a message: cautioning his countrymen about becoming apathetic because of the optimism the Obama administration has brought.

"The danger now is people say, 'Oh, we can relax and let the new president do the work.' The most important part of Obama's inauguration speech was when he said WE have to do the job — all of us."