Julius Eastman (1940–1990) graduated from the Curtis Institute and worked as a pianist-composer-singer virtuoso at SUNY-Buffalo’s Center for the Creative and Performing Arts (CCPA) before building a wide-ranging career in New York City, moving between academic modernism and the Downtown experimental scene, including minimalism, disco, and free jazz. Since the posthumous revival of his music beginning in 2005, Eastman’s reception has been persistently organized around a single genre label: Minimalism. This dissertation argues that the minimalist frame distorts rather than illuminates Eastman’s legacy, and that his performer identity is inseparable from his work as a composer—the two cannot be meaningfully understood apart from one another. Drawing on José Esteban Muñoz’s queer theory of disidentification and Patrick Nickleson’s historiography of minimalism(s), I propose that Eastman the performer-composer worked on and against dominant aesthetic ideology simultaneously, inhabiting and exceeding genre rather than simply conforming to or rejecting it. The dissertation treats performance experience, rehearsal practice, and oral transmission as forms of archival access irreducible to score or recording alone. Chapter 1 develops the theoretical framework, surveying critical receptions of Eastman’s music, challenging the minimalist label’s rhetorical functions, and building the case for disidentification as one productive account of his aesthetic practice, with attention to his “Organic Music” concept on a “continuum.” Chapter 2 examines Piano 2 (1986), Eastman’s only surviving piano solo, a virtuosic modernist sonata whose idiosyncratic score leaves the performer with more questions than answers beyond its determinate pitches and rhythms. Situating the piece alongside the vocal and piano music by several pianist-composers Eastman either worked closely with and/or prominently performed works by, the chapter argues that engaging with these works grants essential interpretive access to Eastman’s score, adding a broader understanding of the piece as modernist to his partially surviving oeuvre’s common associations with minimalism. Chapter 3 offers an extended study of Femenine (1974), combining archival research, analysis of Eastman’s pianism on the premiere recording, and a detailed performer’s guide to the new Schirmer performing edition (2025), for which the author served as editorial advisor and contributed the foreword and performance notes.