This dissertation proposes a framework for analyzing musical interculturality—the processes through which musicians weave together multiple musical and cultural identities through performance—in twenty-first-century music. By attending to the specific sociopolitical contexts of the intercultural environment in which each performer takes part, I challenge multiculturalist assumptions of cultural purity, homogeneity, and authenticity that often undergird music theoretical analyses of non-Western music. My analysis of interculturality centers on musicians whose work risks being excluded from nation-state-based conceptions of cultural authenticity that have dominated music theoretical work on non-Western music. Through three case studies of active Japanese musicians, I explore how a collaborative project between shamisen player Honjoh Hidejirō (本條秀慈郎) and composer Fujikura Dai (藤倉大), performances by shō player Miyata Mayumi (宮田まゆみ), and the music of mixed-race Japanese American singer-songwriter Mitski present heterogeneous possibilities of national and cultural identity. Through close readings of musical recordings, videos, and scores, as well as through interviews and archival work, I demonstrate how cultural and musical identities are constructed through the particular historical and sociopolitical contexts within which performers operate. Focusing on how Honjoh, Miyata, and Mitski complicate and challenge strict dichotomies between Japanese and non-Japanese cultural, national, and musical affiliations, I pay close attention to how intercultural meanings are constructed through their performances, dialogues, and collaborations. In each case study, I argue that an analysis of interculturality necessitates a flexible, interdisciplinary, and transnational methodology that is tailored to the precise historical and sociopolitical circumstances in which the music is being created, performed, and interpreted. By understanding characterizations of Japanese, Western, and Japanese American as contingent categorizations that do not exist a priori but materialize through musical performance, I draw attention to the distinctive ways in which Honjoh, Miyata, and Mitski engage in intercultural music-making. This dissertation challenges essentialist narratives that continue to assume a rigid and homogeneous view of Japanese culture while fetishizing traditional music as a singular marker of authenticity. Given that oppositional binaries between the West/non-West and cultural insider/outsider continue to shape the interpretation of music by non-white non-Euroamerican musicians, I argue that it is crucial for music analysis to confront and complicate—rather than uncritically affirm—these narratives. First, I problematize monolithic and essentialist conceptions of Japanese music. Through analyses of performers who deviate from these narratives, I disconnect expressions of musical identity from ethno-nationalist assumptions and situate ethnicity as one of many factors that shape cultural identity. Second, I interrogate the underlying epistemological frameworks that produce reductive misrepresentations of Japanese music. This dissertation disrupts the underlying Eurocentric epistemological framework that essentializes—and therefore exerts control over—non-Western cultures. I therefore conceive of interculturality not only as an issue of representation, but also as a strategy for challenging the imposed authority of Western systems of knowledge. Third, by analyzing the agency of performers in negotiating and contesting dominant narratives of Japanese ethnic, cultural, and musical identity, I approach interculturality as an embodied and lived phenomenon rather than as only an intellectual analytical endeavor.