Oxford Music Online is the best, most comprehensive site for research on musicians and musical topics. A superb place to start and to gather terminology and sources.
Above the search results from Grove, be sure to also click the provided links to other Oxford titles. Example:
Search for books, e-books, articles, and other materials at Western Oregon University, Summit, and beyond.
NOTE: You can read e-books on any computer or download to your digital device. See: Using eBooks @ WOU
An overview of the Library of Congress (LC) classification for music. Click on a subclass to find more specific call number areas.