Bibliographies

• Music Reference and Research Materials, 5th edition (ML113.D83 1997) - Known simply as "Duckles," after the compiler of the first five editions, this source is an annotated bibliography of books about music. It will provide you with information about more specialized bibliographies and research tools.

Dictionaries

• Bakers Biographical Dictionary of Musicians, Centennial edition (ML105.B16 2001) - Edited by Nicolas Slonimsky, Bakers has become the standard and most authoritative source of biographical information for composers and musicians. The Centennial edition has expanded to six volumes, from a single volume in earlier editions.
• The Harvard Dictionary of Music, 4th ed. (ML100.A64 2003) - The standard English language dictionary of musical terminology and non-biographical information.  The 4th edition is a revision of The New Harvard Dictionary of Music (1992).

Encyclopedias

• Doctoral Dissertations in Musicology Online - A keyword-searchable index to dissertations in musicology, hosted by the American Musicological Society.
• The Classical Music Navigator - A site devoted to 444 composers of Western classical music and their principle works, identifying 111 of the "most influential" of these composers by tracking their influence on subsequent composers.
• All Music Guide - The most extensive discographies of musicians and composers on the Web. Biographies are brief, but cover a wide range of music. Better for international and American popular music and jazz, but the coverage of classical music is quite good as well.