(Reuters) - Bernice Johnson Reagon, an American civil rights activist who used her stirring alto and lyrics to fight racism, died on Tuesday at age 81, her daughter said on Wednesday.

"As a scholar, singer, composer, organizer and activist, Dr. Reagon spent over half a century speaking out against racism and systemic inequities in the U.S. and globally," daughter Toshi Reagon, who like her mother is a musician and activist, said in announcing her death on Facebook.

No cause of death was given.

Born in 1942 in Dougherty County, Georgia, she became active in the civil rights movement at Georgia's Albany State College, an historically Black institution that now is a university, according to a biography on her website.

Reagon was a member of the original Student Non-Violent Coordinating Committee Freedom Singers, formed in 1962. The Freedom Singers performed to raise money for SNCC projects and to rally activists.

In an online SNCC archive, Reagon is quoted describing her early work. At one of the first large meetings she helped organize in Albany, she was asked to lead a song and started an African American spiritual: "Over my head, I see Trouble in the Air." She replaced "trouble" with "freedom," and said that "by the second line everyone was singing." 

In 1973 she formed Sweet Honey in the Rock, an a cappella group of African American women. Among the best-known of the Johnson compositions the group performed was "Ella's Song," with its driving refrain -- "we who believe in freedom cannot rest, we who believe in freedom cannot rest until it comes" -- and other lines inspired by the speeches of another pioneering civil rights figure, Ella Baker. "Ella's Song" can still be heard at demonstrations today.

She also was a music scholar who studied the African American spiritual. She was professor emeritus of history at American University and curator emeritus at the Smithsonian's National Museum of American History.

(Reporting by Daniel Trotta; editing by Donna Bryson and Michael Perry)