The WSU Library uses the Library of Congress Classification System to organize most of its books. The LCC system organizes books into twenty-one broad subject areas. Each letter and number in the call number signifies specific topics. For example, M is for Music, MT949.5 will include books about Whistling.
The following .pdf file (link) will provide a general outline of items cataloged in the M section:
Here's how to find a book when the WSU Library doesn't have it: