Call numbers begin with a letter which stands for the subject:
- M = Scores
- ML = Music Literature
- MT = Music theory, Music pedagogy, and Music instruction
Next comes a number which stands for a narrower subject:
- M 23 = Piano sonata scores
- ML 410 = Composer biographies
- MT 425 = Horn studies and exercises
This is followed by a decimal point, a letter, and a number which stands for the composer or author:
- M 23 .M939 = Mozart piano sonatas
- ML 410 .B853 = A biography of Benjamin Britten
- MT 425 .G3 = Horn etudes by Gallay
Sometimes these are followed by other letters or numbers such as op., no., or other work number:
- M 23 .M939 K.310 = Mozart piano sonata, K. 310
- MT 425 .G3 op.57 = The opus 57 horn etudes by Gallay