Included within Oxford Music Online. The New Grove Dictionary of Music and Musicians is the authoritative encyclopedia of music. Major articles on composers, performers, instruments, the musical life of countries and major cities, musical forms, terms and concepts.
Also included in Oxford Music Online. Articles on operas (by title), composers, singers, librettists, opera houses, national opera traditions, and opera-related terms. Indexes of role names and incipits (first lines) of arias and ensembles.
Available in print: [Dunbar Reference ML 105 .B16 2001]. Brief biographies (one paragraph to a few pages) of persons from all aspects of musical life. Has entries for many musicians not covered in Grove.
Available in print: [Dunbar Reference ML 100 .M92 1994]. The major German music encyclopedia. Has many persons not in Grove or Baker's. Text is in German, but you can make out enough to get birth/death dates, etc.
Available in print: [Dunbar Ref Bookcase 1 AE5 .E363 2007]. A good place to look for biographical information on poets whose texts have been set to music.
Provides authoritative biographical articles on persons who have shaped the British past. Includes bibliographic references. No living person is included. Entries in the online Dictionary appear about four years after the person's death.
Available in print: [Dunbar Reference ML128 .S3 E8]. Arranged by language and time period. Gives voice range and tessitura, and brief description of song. Indicates published collections that include the songs.
Available in print: [Dunbar Reference ML102 .O2 B62]. List of roles and arias from over 1000 operas, cross-referenced by voice category, composer, and opera.