This dissertation examines aspects of the creative practice of Muhal Richard Abrams, composer, improviser, pianist, and cofounder of the Association for the Advancement of Creative Musicians (AACM). Abrams’s work intersects with various facets of creative music. I focus on free improvisation, both as a stand-alone performance and in conjunction with through composed music, his engagement with writings by theorist Joseph Schillinger, and his work as a composer. This study provides an historical overview of Abrams’s life and output, supplies analytical accounts of his music and creative practice, contributes to critical issues in music theory and analysis through these examinations, and diversifies the music, musicians, and topics that comprise the discipline of music theory. My examinations position Abrams as an important figure in twentieth century music, both improvised and composed, and expand studies in music theory and analysis. I offer new perspectives on and a framework for the analysis of free improvisation and intra-ensemble interaction, challenge traditional binaries between music theory and black experimental music, explore the influence of Schillinger’s theoretical treatise, The Schillinger System of Musical Composition ([1946] 1978), on Abrams’s work as a composer, explicate a set of idiosyncratic theoretical publications to suggest an underground genealogy of music theory, and posit an analytical vista that sits at the intersection of music performance, disability, and critical race studies. My overview of Abrams’s life and work draws on historical scholarship to tease out details of his development and practice in Chicago and New York, and analyzes contemporaneous articles from magazines, newspapers, and journals in order to provide a snapshot of the reception of Abrams’s work and the various scenes that he traversed. In response to Abrams’s individual approach to interactive free improvisation, which functions as either a stand-alone performance or alongside composed music, I employ the concept of affordances from ecological psychology. My affordance based analytical framework facilities a reappraisal of musicians’ interactions during free improvisation and also theorizes the relationship that emerges when free improvisation is preceded and/or followed by composed material. I analyze Abrams’s improvised duet with Fred Anderson, “Focus, ThruTime…Time—>” (2011) and his quartet rendition of “Munktmunk” (1987) to illustrate my framework and elucidate the richness of these performances. I perform a close reading of Schillinger’s theoretical treatise to suggest resonances between Abrams’s creative practice and the text. I do not aim to elect Schillinger as a kind of fountainhead for Abrams’s practice. Rather, I argue that the numerous resonances between Schillinger’s text and Abrams’s practice connote reasons why the treatise strongly appealed to Abrams, such that he employed it both compositionally and pedagogically for a large portion of his life. I extrapolate from this discussion to outline and theorize an underground genealogy of music theory that represents a more diverse set of music theoretical practices than is often discussed in the discipline. Finally, I analyze composed portions of four works by Abrams: “Inner Lights” (1985), “Charlie in the Parker” (1977), “Hearinga” (1989), and “Piano Duet #1” (1987). My analyses of the first three of these pieces intimate the presence of some of Schillinger’s theoretical principles. Abrams does not simply realize Schillinger’s theoretical method in his work, but rather maintains artistic agency by selectively filtering those suggestions through his own pluralistic aesthetic. Finally, I combine recent work on disability in music and critical race theory to analyze “Piano Duet #1,” in which the two pianists’ bodies are restricted in performance. This analysis offers a generative reappraisal of music performance and disability studies in light of race while also elucidating some of the richness of Abrams’s composition.