Try these first...
- Cambridge Histories Online: Music (9 broad histories of music; search within the text of each volume)
- Oxford Bibliographies (Oxford Bibliographies offers exclusive, authoritative research guides. Combining the best features of an annotated bibliography and a high-level encyclopedia)
- Oxford History of Western Music ONLINE, an amazing narrative of the evolution of Western classical music.
- Oxford Music Online (Includes: Grove Music Online, The Oxford Companion to Music, The Oxford Dictionary of Music)
- RISM OPAC (Includes: A/II: Music Manuscripts after 1600, A/I: single prints & new entries for B/I: Collections. More about the content...)
- Continuum Encyclopedia of Popular Music of the World: Locations (via Credo Reference)
- Continuum Encyclopedia of Popular Music of the World: Media, Industry, and Society
- Continuum Encyclopedia of Popular Music of the World: Performance and Production (via Credo Reference)
- Grove Dictionary of American Music (2nd edition Online)
- ProQuest Dissertations & Theses Global
- Networked Digital Library of These and Dissertations
Search this database for international dissertations and theses. WorldCat (OCLC) is also a good option.
- Emusicquest: Music In Print (scores)
- The Faber Companion to 20th Century Popular Music (via Credo Reference)
- The Garland Encyclopedia of World Music Online (via Alexander Street Press)
- Harvard Biographical Dictionary of Music (via Credo Reference)
- Harvard Dictionary of Music (via Credo Reference-provides definitions of musical terms)
- Hofmeister XIX (Free on the Web)
Index to printed music, music books & periodicals, illustrations, portraits & busts of composers published or produced between 1829-1900.
- Index to Printed Music
- International Dictionary of Opera (via Gale Biography Reference Center)
- Metropolitan Opera Encyclopedia: A Comprehensive Guide to the World of Opera
- The New Penguin Dictionary of Music (via Credo Reference)
- Orchestral Music Online (instrumentation and durations for more than 7000 orchestral works by more than 1000 composers; links to publishers)
The RIdIM database is designed to facilitate discovery of music iconography images by registered researchers, and the description of such images by registered cataloguers.
- RISM A/II: Music Manuscripts (1600-1800) in British and Irish Libraries
- US-RISM Libretto Database (13,000+ citations for libretti in the Schatz Collection at the Library of Congress), available through the University of Virginia Library's online catalogue, Virgo (include keywords such as "operas" or "librettos" to find records). ***Note that the Schatz Collection microfilm is held in the Yale Music Library, Microforms, Reel 1904.***
Free Reference Sources Online...