"Music and the literature of music. At the outset of this discussion the reader must make a clear distinction between what we are calling the 'literature of music' or 'books about music' and what we designate al 'scores'. The former terms embrace historical and biographocal works, books and the theory and art of music, essays, etc., while the latter word applies to the printed or manuscripted form of the musical composition. When classifying a music collection, it is desirable to segregate those two classes."
WALLACE, RUTH. The Care and Treament of Music in a Library. Chicago: American Library Association, 1927.