Emahoy Tsege-Mariam Gebru (1923-2023) was an Ethiopian composer, pianist, and nun. Despite international acclaim, a devoted cult following, and widespread media influence and coverage, the absence of critical discourse about Emahoy Tsege-Mariam has maintained about her an aura of exotic mystery. In redress, this dissertation establishes a critical (and culturally contextualized) biography, stages a stylistic analysis, discusses challenges of musical interpretation, and catalogs her output. Drawing from a wide range of archival, historical, and music-theoretical sources, as well as interviews and practical fieldwork, this comprehensive study reconfigures Emahoy Tsege-Mariam as a cosmopolitan, modernist, and concretely historical figure, out of the realm of legend.