Discographies are subject-specific lists containing various amounts of information about sound recordings. They can be in book or journal article form, a concise list at the end of a book or article on a given subject, or on the Web.
If you want to locate music from a particular era, consult a music chronology (timeline). Use the catalog and the subject "music chronology." Some of these resources can help you find music by geographical area as well. After you have located the name of a composer, performer, or work, search for recordings in the UMD catalog.