Reference works include encyclopedias, thematic catalogs, indices, and guides to research. Many are printed editions that can be found in the reference section of the Fine & Performing Arts Collection. There are important electronic versions, as well, like Oxford Music Online.
A Guide to Research is a book-length bibliography of scholarship on a composer, genre, or special topic. They are excellent resources for quickly learning about the breadth and depth of research on a topic. It is important to note the year of publication because any scholarship published after this date cannot be included.
The Fine & Performing Arts Collection has hundreds of Guides to Research on a wide variety of music topics. Here are a few examples.
Thematic Catalogs are complete lists of works by a composer or in a genre. They include incipits, the opening musical gesture of a piece, and other important musical themes and motives.
Here are a few examples of thematic catalogs available at Rod Library.