Bernice Johnson Reagon was an American civil rights advocate who used her stirring alto to fight racism. Her daughter announced on Wednesday that she died at the age of 81 on Tuesday.

Toshi Reagon announced her mother's death on Facebook. She is also a musician.

The cause of death has not been determined.

According to her biography, born in Dougherty county, Georgia in 1942, she was active in the civil right movement while attending Albany State College in Georgia. This historically Black institution is now a university.

Reagon was one of the original Freedom Singers from the Student Non-Violent Coordination Committee, which were formed in 1962. The Freedom Singers were formed to raise funds for SNCC and rally activists.

Reagon's early work is described in an online SNCC archives. Reagon was asked to sing at one of the large meetings that she organized in Albany. She began a spiritual by singing "Over my Head, I See Trouble in the Air" and changed "trouble' with "freedom".

Sweet Honey in the Rock was formed in 1973 by African American women. The group's most famous composition by Johnson was "Ella's Song", with its driving refrain - "we who believe freedom cannot rest" - and other lines inspired from the speeches of another civil rights pioneer, Ella Baker. The song "Ella's Song", which is still heard today at protests, was composed by Johnson.

She was also a musicologist who studied African American spiritual. She was professor of history emeritus and curator emeritus of the Smithsonian National Museum of American History. (Reporting and editing by Donna Bryson, Michael Perry and Daniel Trotta)