NASHVILLE (AP) — Bernice Johnson Reagon, a musician and scholar who used her rich, powerful contralto voice in the service of the American Civil Rights Movement and human rights struggles around the world, died on July 16, according to her daughter's social media post. She was 81.

Reagon was probably best known as the founder of the internationally renowned African American female a cappella group Sweet Honey in the Rock, which she led from 1973 until her retirement in 2004. The Grammy-nominated group's mission has been to educate and empower as well as entertain. They perform songs from a wide range of genres that include spirituals, children's songs, blues and jazz. Some of their original compositions honor American civil rights leaders and international freedom movements like the struggle against apartheid in South Africa.

"She was incredible," said Tammy Kernodle, a distinguished professor of music at Miami University who specializes in African American music. She described Reagon as someone "whose divine energy and intellect and talent all intersect in such a way to initiate change in the atmosphere."

Reagon's musical activism began in the early 1960s when she served as a field secretary for the Student Non-Violent Coordinating Committee and became an original member of its Freedom Singers, according to an obituary posted on social media by her daughter, musican Toshi Reagon. The group reunited and was joined by Toshi Reagon to perform for then-President Barack Obama in 2010 as part of a White House performance series that was also broadcast nationwide on public television.

Born in Dougherty County outside of Albany, Georgia, in 1942, Reagon attended music workshops in the early 1960s at Tennessee's Highlander Folk School, a training ground for activists. At an anniversary gathering in 2007, Reagon explained how the school helped her see her musical heritage as something special.

"From the time I was born, we were always singing," Reagon said. "When you're inside a culture and, quote, 'doing what comes naturally to you,' you don't pay attention to it. ... I think my work as a cultural scholar, singer and composer would be completely different if I had not had someone draw my attention to the people who use songs to stay alive, or to keep themselves together, or to lift up the energy in a movement."

While a student at Albany State College, Reagon was jailed for attending a civil rights demonstration and expelled. She later graduated from Spellman College. She formed Sweet Honey in the Rock while a graduate student of history at Howard University and vocal director of the D.C. Black Repertory Company.

Reagon recorded her first solo album, "Folk Songs: The South," with Folkways Records in 1965. In 1966 she became a founding member of the Atlanta-based Harambee Singers.

Reagon began working with the Smithsonian Institution in 1969, when she was invited to develop and curate a 1970 festival program, Black Music Through the Languages of the New World, according to the Smithsonian. She went on to curate the African Diaspora Program and to found and direct the Program in Black American Culture at the National Museum of American History, where she was later a curator emeritus. She produced and performed on numerous Smithsonian Folkways Recordings.

For a decade, beginning in 1993, Reagon served as distinguished professor in history at American University in Washington, later becoming a professor emerita.

We assume that music was always a part of civil rights activism, Kernodle said, but it was people like Reagon who made music "part of the strategy of nonviolent resistance. ...They took those songs, they took those practices from inside the church to the streets and the jail cells. And they universalized those songs."

"What she also did that was very important was that she historicized how that music functioned in the civil rights movement," Kernodle added. "Her dissertation was one of the first real studies of civil rights music."

Reagon received two George F. Peabody Awards, including for her work as principal scholar, conceptual producer and host of the Smithsonian Institution and National Public Radio series "Wade in the Water: African American Sacred Music Traditions."

She was also the recipient of the Charles E. Frankel Prize, Presidential Medal, for outstanding contributions to public understanding of the humanities, a MacArthur Fellows Program award, and the Martin Luther King Jr. Center for Nonviolent Social Change Trumpet of Conscience Award.