Throughout the 1910s and 1920s, when much of the world's gaze was fixated on the innovative technologies and striking urban environments of the United States, a " machine-age" aesthetic became significant in the struggle for American composers to compete with Europe's domination over " cultivated" music. By mixing machine themes with music, composers like George Antheil challenged conventions, sparked debates, and questioned boundaries such as those between the past and the future of music, European and American culture, human performers and " mechanical" instruments, and the esteemed space of the concert hall and the " noise" of industry and the metropolis. Entangled in many of these debates, which surfaced throughout popular, academic, and avant-garde discourses, were questions about the evolving roles of pianos and automatic pianos both in the concert hall and at home. The percussive and mechanistic aspects of the piano, the surge of innovations in automatic piano technologies, and the production, marketing, and design of the instruments all made the piano an ideal vehicle for both creating and / or embodying machine-inflected music and imagery. From the wide range of experimentation with its form, function, technique, and identity, the piano became a locus for some of the era's most fervent social and cultural debates regarding the mechanization, urbanization, and " Americanization" of art and society. This dissertation examines the importance of the machine aesthetic, and especially the " piano as machine" idea, in the construction of an American brand of modernist music throughout the 1920s. Rhetoric surrounding both American avant-garde works and evolving piano technologies often mirrored the anxiety and elation that arose from the increasingly ubiquitous encounter between humans and machines. Just as automatic pianos were cast as either " soulless machines" or the beginning of a utopian future, so were the tone clusters of Henry Cowell, for example, described in reviews as either shards of mechanistic noise and monotony or pieces of futuristic brilliance. Critics paid particular attention to how effective American composers were at " expressing America," with its fast-paced cities and modern technologies. The successes and failures of both the piano industry and machine-inflected American modernist music were directed by the larger social adjustment to a quickly changing world. By the early 1930s, both the machine aesthetic and the automatic piano went out of vogue, but they remain important vehicles for understanding the experimentation, achievement, and disillusionment of the American modernist music scene in the 1920s, and represent the conflicts and contradictions of a time of abrupt transitions.