One of the challenges with doing research on geography of music (or geography in music, or ecomusicology) is how cross-disciplinary and interdisciplinary the sources are. The lists of subjects, terms, journals, and suggested databases is selective and far from comprehensive. The most logical recommendation is that once you've found an article or a book that addresses your topic (or one aspect of your topic), examine any assigned subject terminology and use that terminology in another search to find more on that topic.
Suggested music databases:
These multidisciplinary resources offer citations and often full-text for journal articles, books, and dissertations. They're wonderful for searching topics that cross traditional disciplinary boundaries, but one can also get lost in either a wealth of citations (that may or may not be relevant) or frustrated because there's nothing for that particular search. With multidisciplinary resources, one often needs to try broader search terms and then narrow or filter the search results.