Music call numbers in the Library of Congress Classification (LCC) system are subdivided by format.
Music literature is shelved under ML (note that we only have a few items, primarily librettos, in the music library under ML; most music literature is held in the main library and is shelved using the Dewey Decimal system). Music education items are shelved under MT. These items are located in the Music Education Room and include both books (e.g. teaching manuals) and scores (e.g. studies and methods). Scores are shelved under M in the main part of the music library.
The basics of how LCC works
Scores are classified primarily according to medium of performance. Various subcategories are also used, including number of performers, genre, and form. For example, full scores of operas are shelved under M1500 while opera vocal scores are shelved under M1503. As someone looking for a score, consider if you need the full score or the vocal score—or perhaps either will do?
Remember that LCC relies primarily on medium of performance. The system does not always distinguish between ‘classical’ and ‘popular’ music. For example, you will find both opera and musical vocal scores shelved under M1503; however, you will find that art song and popular song are shelved under different call numbers. This can get tricky at times—remember that what you may consider an art song, LCC might consider a popular song!
Note that the LCC call number also gives you other information about the score. Most duos will have a call number in the M200s while quintets will be shelved under the M500s.
LCC often shelves original works and arrangements under different call numbers. You may need to check under both call numbers if you are not sure whether or not the score you are looking for is an arrangement.
Remember, you can always search WorldCat Discovery for specific titles to find the call numbers to start browsing. You can also search by call number.