Barbara Dane has sung with the best like Louis Armstrong, Earl Hines, Jack Teegarden and may others. From her bio at http://www.barbaradane.net/Home.html:

Born into a white middle-class family, as a child Dane sang and played piano in Sunday school and also learned to play guitar. From the mid-40s she became involved with the labor, civil rights and feminist movements. She sang folk and jazz, working with Pete Seeger, Kid Ory , George Lewis , Turk Murphy and others, appearing at festivals and on television, and she even hosted her own show in San Francisco. Dane appeared at many prestigious venues and shared bills with distinguished performers, including Louis Armstrong, Memphis Slim, Lightnin’ Hopkins and controversial comedian Lenny Bruce. In 1959, she recorded with Earl Hines and toured with Jack Teagarden ‘s band, and continued her high profile on television, radio and in concert, throughout the 60s and 70s. In this time she became increasingly involved in political causes, including demonstrations and marches in support of the civil rights movement and in protest against American military involvement in Vietnam. She concentrated her musical efforts on singing at fund- and consciousness raising gatherings in America, Spain, Cuba and Italy, and traveled to Vietnam in 1975. Dane’s decision to ally her singing to political causes has tended to keep her from the general audience. Her folk singing has a strong sense of commitment and she is also a sound and convincing singer of the blues. Her records are hard to find but worth seeking out.