Baker's Biographical Dictionary of Musicians. The highly respected Baker's covers groups as well as individuals. 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.
MUSICMEDIA REFERENCE ML105 .B16 2001
Continuum Encyclopedia of Popular Music of the World. Ed. by John Shepherd et al. New York: Continuum, 2003– . 9 vols.
Hischak, Thomas S. The Tin Pan Alley Song Encyclopedia. 2002.
MUSICMEDIA REF ML102 .P66 H57 2002
Lax, Roger, and Frederick Smith. The Great Song Thesaurus. 2d ed. 1989.
MUSICMEDIA REF ML128 .S3 L4 1989
Oxford Music Online provides access to the Encyclopedia of Popular Music as well as to Grove Music Online, which covers jazz and popular music and includes the content of the New Grove Dictionary of Jazz.
The Popular Music Research Guide lists additional reference works.
Grove Music Online includes the content of The New Grove Dictionary of Opera (print version: MUSICMEDIA REF ML102 .O6 1992)
Peattie, Anthony, and the Earl of Harewood. The New Kobbé’s Opera Book. 11th ed. 1997.
GENERAL MM-REF MT95 .K52 1997
A standard one-volume reference work.
Gänzl, Kurt. The Encyclopedia of the Musical Theatre. 2nd ed. 3 vols. 2001.
MUSICMEDIA REF ML102 .M88 G3 2001
Other Important Works
Loewenberg, Alfred. Annals of Opera, 1597-1940. 3d ed. 1978.
MM-REF ML102 .O6 L6 1978
A listing of operas by date of first performance, for the period 1597 through 1940, with details about the premiere and subsequent performances.
Lynch, Richard Chigley. Musicals?: A Complete Selection Guide for Local Productions. 2nd ed. 1994.
MM-REF ML19 .L9 1994
Norton, Richard C. A Chronology of American Musical Theater. 3 vols. 2002.
GENERAL MM-REF ML1711.8 .N3 N67 2002
Chronological listing of performances, with information on the creators, original cast, and a list of every song in the show. Index of songs, selected index of persons.
Parsons, Charles H., and Edwin Mellen Press. The Mellen Opera Reference Index. 1986—.
GENERAL MM-REF ML102 .O6 P55 1986
v. 1-4. Opera composers and their works -- v. 5-6. Opera librettists and their works -- v. 7-8. Opera premieres : a geographical index -- v. 9. Opera subjects -- v. 10-12. Opera discography -- v. 13-14. Opera premieres : an index of casts -- v. 15-16. Opera premieres : an index of casts, performers -- v. 17-18. An opera bibliography -- v. 19. Opera premiere reviews and re-assessments : a listing (2 v.) -- v. 20. An opera videography -- v. 21. Printed opera scores in American libraries (3 v.) -- v. 22. Recent international opera discography (4 v.) -- v. 23. Recent international opera discography. Performers (3 v.) -- v. 24-26. Recent international opera discography: 2003–2007 updates (in 3 vols.).