There are a variety of ways of locating books about music. Common pathways include searching for books using the Libraries catalog and browsing the shelves by call number.
You can search for books within the Libraries catalog (http://www.lib.purdue.edu) by Author, Title, Keyword, and Subject. Catalog tutorials can be found here: http://www.lib.purdue.edu/hsse/researchguides/lib_homepage_and_catalog.html.
To search by topic, search using Keywords and Subject Headings.
Searching by keyword is akin to using a web search engine such as Google. Words you use to search will return books with those same same words. For example, if you search using the word acoustics, you will get a list of books about acoustics. If you search with the words "music theory" (quotes included) you will get a list of books about music theory.
Keyword searching returns books by raw text matching. At times this is problematic as words often have multiple meanings. Consider the word fox, which could refer to the mammal, people with that last name - Michael J. Fox, and corporations - Fox Broadcasting Company, Fox News Channel, etc. To limit your search to one of these meanings, you would use subject headings. For example, if you wanted to search for fox the animal, you would search with the word "foxes" as a Subject Heading.
Here are some common subject headings in music:
The Purdue University Libraries utilizes two systems for classifying and locating books - the Dewey Decimal Classification system and the Library of Congress Classification system. All books acquired after January 2009 are classified according to the Library of Congress Classification system.
Books about music are classified under the 700's (Arts and Recreation), and more specifically between 780-789:
Books about music are classifed under the class M. There are three subclasses within the main class: