Kahn grew up in State College, Pennsylvania. When he was 15 his family moved to the Washington, DC area, where he graduated from Bethesda-Chevy Chase High School. His grandfather Gabriel Kahn, his mother Rosalind Kahn, and his father Benjamin Kahn, a rabbi, instilled a strong sense of the family's Jewish heritage as well as teaching him the rudiments of rhythm and harmony as a child. His uncle, Arnold Aronson, executive secretary of the Leadership Conference on Civil Rights, helped inspire and shape Kahn's career. Kahn earned a bachelor's degree from Harvard University. In 1995 he completed a Ph.D. in American Studies from the Union Institute.
Kahn moved to the south as an activist in the Civil Rights Movement, and he now lives in Charlotte, North Carolina. Kahn is the founder and former director of Grassroots Leadership, a non-profit organization that advocates for several causes, including prison reform, improved immigration detention policies, and violence prevention. He retired May 1, 2010. Most of the profits from Kahn's musical performances benefit this group. He has also been involved with Save Our Cumberland Mountains, an environmentalist group opposed to strip mining in Appalachia.
Though Kahn writes songs about a variety of topics, he is especially known for songs about workers and their families, like "Aragon Mill" (1974). He frequently writes songs, and occasionally performs, with singer-songwriter and multi-instrumentalist John McCutcheon. Kahn usually accompanies himself on a steel-string acoustic guitar, played with brass fingerpicks.
Reviewing Kahn's 1974 New Wood album in Christgau's Record Guide: Rock Albums of the Seventies (1981), Robert Christgau observed "willfully austere Appalachian music" and songs that are "correctives every one (despite an occasional baldness of instructional intent) to the romanticizations of Southern pastoral individualism that are currently so profitable." He went on to call Kahn "an aficionado of poor-white virtues, but not at the expense of his vivid understanding of the labor, sadness, frustration, and small-mindedness that go along with them."
By the time of Kahn's 1979 record Home, Christgau had called him "the most gifted songwriter to come out of the folkie tradition since John Prine", possessing a political outlook in songs that are nonetheless "personal, their overriding theme the emotional dislocations of working far from home." While identifying Kahn's asset as living among ordinary people rather than the folk subculture, the critic credited Kahn's "understated colloquial precision" and concluded that, "some will consider the all-acoustic music thin (it's often solo or duet, twice a cappella) and the voice quavery. I find that both evoke the mountain music of the '20s in a way that makes me long for home myself, and I'm from Queens."