St. Olaf College Libraries uses the Library of Congress Classification system to create call numbers. Here are some useful call numbers for singers:
M 2 Collected anthologies (for example, M2 .R3 is Recent Researches in the Music of the Baroque Era)
M 3 Collected works of individual composers (for example, M3 .D35 is the complete works of Debussy)
M 1520-1609 Secular choruses
M 2010-1017.6 Sacred choral services
M 2020-2114.8 Sacred choruses
ML 410 Biographies of composers
ML 420 Biographies of singers (alphabetical by last name)
ML 1400-1460 Books about vocal history and criticism
MT 820-893 Vocal instruction and study (techniques, method books. etc.)
ML 1400-1460 Books about vocal history and criticism
MT 820-893 Vocal instruction and study (techniques, method books. etc.)