Welcome! I hope this guide will get your music research off to a good start.
This is particularly helpful for composers (or genres or results in general) with many "hits" in the catalog search.
From here you can see if an item is available, where in the library it is shelved, and the call number (exactly how it's filed on the shelf).
Yes, these call numbers have a specific organizational scheme. For example, composer biographies are assigned call numbers starting with ML410. Bibliographies of composers and thematic catalogs are assigned call numbers starting with ML134. Want to know more about the Library of Congress call number system for music?