This article uses the concept of aesthetic identity to interrogate the relationship among musical genres, social movements and racial identity. American folk music has at some times subverted and other times reinforced the categorical boundaries between blacks and whites in twentieth-century United States. Aesthetic identity is the cultural alignment of artistic genres to social groups by which groups come to feel that genres represent our or their art, music, and literature. Genre boundaries then become social boundaries. Folk music inverts the usual relationship of genre and social boundaries. Folk music is always the culture of some other, either racial, regional, class, or national. Before it was called folk music, American vernacular music was much more racially integrated than the society around it, creolized across a spectrum from predominantly European to predominantly African- influenced, but with most exhibiting both. Before the era of commercial recording, black and white musicians sang the same music, learned techniques and songs from each other, and shared a social world of performance. The concept of folk music was created by academic elites, but remained unfamiliar to most people until the organized left took it on as a cultural project in the late 1930s and 1940s. Both academic elites and political activists constructed the genre as an alternative to the racialized genres that the commercial recording industry had dubbed race records and hillbilly music. American communists and their allies were especially self-conscious about using folk music as an instrument of racial solidarity in a particularly racially polarized era. Submerged by McCarthyism until the 1960s, folk music was revived as a racially unified genre, but quickly became whitened. My explanation for why the folk revival was so white revolves around three factors: the continuing legacy of commercial racial categories, the failure of the New Left to control music through a cultural infrastructure as effectively as had the old left, and the cultural momentum of an understanding of folk music as the music of the other at a time when blacks were trying to enter a system that white middle-class youth were rejecting.