Call number ranges for choral music:
M 1529-1609 Secular choral
M 1611-1624 Secular vocal
M 1999-2199 Sacred choral & vocal
M 2000-2003 Oratorios
M 2010-2013 Masses, requiems, etc.
M 2020-2023 Cantatas and other works
M 2038-2058 Anthems
Sources for free scores online:
Classical Scores Library, volume 1 contains more than 50,000 scores in PDF files for printing. Search specific composers, works, genres, instrument, time periods, etc., or browse the collection. Links to the audio recordings in Classical Music Library allow users to listen while viewing the score.
Books on choral music are at these call numbers:
See also the Composers tab above for finding music by and information about specific composers.
Some useful library resources:
Choral Music by 
Choral Repertoire by
Choral Repertoire is the definitive and comprehensive one-volume presentation of the canon of the Western choral tradition. Designed for practicing conductors and directors, students and teachers of choral music, amateur and professional singers, scholars, and interested vocal enthusiasts, it is an account of the complete choral output of the most significant composers of this genre throughout history. Organized by era (Medieval, Renaissance, Baroque, Classical, Romantic, and Modern), Choral Repertoire covers general characteristics of each historical era; trends and styles unique to various countries; biographical sketches of over 500 composers; and performance annotations of more than 5,000 individual works. This book will be an essential guide to programming, a reference tool for program notes and other research, and, most importantly, a key resource for conductors, instructors, scholars, and students of choral music.
A Conductor's Guide to Choral-Orchestral Works, Classical Period by 
Historical Dictionary of Choral Music by Two sources for translations are below. Recordings can also be a good source for texts and translations.
Translations and Annotations of Choral Repertoire by Collections with a significant amount of choral music are:
Search these as titles in the library catalog to see what is available.
Choral Journal
Choir & Organ
Voice of Chorus America
These are in the Current Periodicals area for browsing; back issues in Periodicals stacks. We have access to many more periodicals via article databases.