Throughout jazz history, improvisation has been central to the music’s aesthetic and social force. From the polyphonic group extemporizations of early styles, through the featured solos within Swing Era arrangements, to bebop’s harmonic steeplechase or the open form experiments that followed, jazz musicians have privileged departures from through-composed scores and fixed musical texts. This essay considers the social, ideological, and aesthetic stakes of these departures, exploring how the music’s emphasis on improvisation constitutes both an ongoing impetus for artistic innovation and a vital challenge to the American status quo. By opening up a cultural space for validating otherwise marginalized Black innovators, improvisation has offered resources for hope, social transformation, and Black mobility. It has also enabled an ongoing critique of existing discourses, subjecting the rigidity of white supremacy, Eurocentrism, or sexism, for instance, to reformulation through an articulation of other possible futures.