Start with Oxford Music Online, which contains several music reference sources, most notably Grove Music Online, to get an overview of a topic, genre, etc. For topics in world music, Garland Encyclopedia of World Music Online is also a good place to start. Consult relevant articles and their bibliographies. [You may have already done this initial work in selecting a topic and getting background information.]
Keep in mind, though, that reference sources like this are not continuously updated. Search literature databases like RILM and Music Index Online (separately or simultaneously) for more recent books, book chapters, articles, and dissertations.
Search the Library Catalog (for books) and Articles & Full Text (for articles) to locate specific items cited in bibliographies, and to see what else may be available.
*** If you are looking for a chapter from a book, search the title of the book rather than the title of the chapter. If you are looking for a journal article, search the title of the article, rather than the title of the journal.