This paper explores bi-musicality in modern Japan, and compares it with bilinguality at societal and individual levels. It considers the usefulness and limitations of the comparison of language and music. It establishes a model of musical competence as a preliminary to considering bi-musical competence, and schematizes the differences between Japanese and Western musical cultures for this purpose. In considering the relevance of bilingualism to the development of bi-musicality as an aspect of bi-culturality, I will argue that bilingualism as such is not so relevant to Japanese music, because early in Japan s modern period Western music was effectively translated into Japanese culture. The application of the concept of bi-musicality to music in modern Japan offers a new perspective on Japan s musical modernity.The discussion will focus first on the societal level, that is, Japan as a bi-musical culture. Then some individual case studies will be presented of people whose bi-musicality has been central to their musical activity. This will lead to some tentative conclusions about the extent and nature of bi-musicality in Japan. (c) The Author(s) 2012.