Argentine singer Mercedes Sosa—known as the Voice of Latin America because of her proclivity to sing about social justice—died on Sunday at the age of 74. An official announcement posted to her website said, "On this day, in the city of Buenos Aires, Argentina, we must inform you that Mrs. Mercedes Sosa, one of the greatest artists of Latin American popular music, has left us."

Born on July 9, 1935, in San Miguel de Tucumán in a northwestern Argentine province, Sosa gained fame in the 1950s. She was one of the preeminent figures of the Nueva Canción movement, which combined traditional folk music with popular rock music and progressive lyrics. "Her voice always carried a profound message of social engagement through folk-roots music, without prejudice," proclaimed her website.

Sosa made more than 40 albums throughout her career and performed at the Sistine Chapel at the Vatican and New York's Carnegie Hall. "She lived her 74 years to the fullest," said Sosa's son, Fabian Matus. "She had done practically everything she wanted; she didn't have any type of barrier or any type of fear that limited her."

Three days of national mourning were declared by Argentine lawmakers. Sosa's coffin is at Argentine congress and will be reopened at 9:30 a.m. for a final good-bye before her burial at the Chacarita cemetery later today.