Grove Music Online (Accessed through Oxford Music Online)
The primary English-language reference source for music, with over 47,000 articles. Comprises the full text of the New Grove Dictionary of Music and Musicians, 2d ed. (MM-REF ML100 .N48 2001), the New Grove Dictionary of Dictionary of Opera (MM-REF ML106 .N5 O6 1992) and the New Grove Dictionary of Jazz, 2d ed. (MM-REF ML103 .J3 N48 2002), plus updates to some articles.
Harvard Dictionary of Music, 4th ed. Don Michael Randel, ed. Cambridge, MA: Belknap Press of Harvard University Press, 2003.
An authoritative source for definitions and concise articles on musical topics and terms. No articles on people. Online access is through Credo Reference Library. Print version: Musicmedia REF ML100 .H37 2003.
Baker's Biographical Dictionary of Musicians, Centennial ed. 6 vols. Nicolas Slonimsky, ed. emeritus. New York: Schirmer Books, 2001.
Recognized as the standard biographical dictionary in English, Baker's covers groups as well as individuals. Articles are usually more concise than those in Grove's. Of special interest are the indexes by nationality and genre (actually by historical period for people in art music) and the index listing women composers and musicians.
Print version (comprehensive): Musicmedia Reference ML105 .B16 2001.
Online version (partial coverage): Gale Biography in Context—contains most of the articles but inexplicably lacks some important ones. Contains none of the bibliographies and work-lists that the print version incorporates in the biographies.
Oxford Bibliographies Online. Music.
Guide to scholarly literature in music. The initial release contains articles on 50 topics and individuals, with extremely useful bibliographies of recommended resources. Cross-searching with other modules of Oxford Bibliographies Online is possible in Advanced Search. Highly recommended if the available articles pertain to your topic.