To find resources on sacred music in the catalog, select the "Subject" search on the Advanced Search page. Some of the terms you would use include "Church music" or "Choruses."
Depending on your topic, you can narrow down your searching even further by adding subdivisions. For example, under the "Church music" subject search, you could focus the search in these different ways:
Church music - Catholic Church
You could also change the results by the format of the book, adding terms like "Encyclopedias," "Handbooks, manuals, etc.," and "Dictionaries" to the end, bringing back just those types of items.
Broadening your search could be beneficial as well. Here are some general topics that could provide worthwhile books:
Music in Christian Worship by 
Sacred Song in America by BR- Christianity
BS- The Bible
BX- Christian Denominations
M- Music
ML- Literature on music
MT- Instruction and study
