Ethnomusicology often relies heavily on other disciplines, particularly anthropology and area culture studies. This is because, unlike western art music, many of the cultures being studied have non-literate traditions and require scholars to immerse themselves in the daily life of the people being studied to get a better sense of the role music plays. These materials are not generally found in the Music and Performing Arts Library so you may have to visit other collections to find them.
The Education and Social Science Library is probably the best place on campus to find anthropological materials. They have created a subject guide on Anthropology which should give you a good jumping off point.
Most of the area studies libraries have been recently consolidated into the International & Area Studies Library but web portals to more information about specialized collections still exist: