Brief but informative biographies can be found in:
For music terminology, styles and forms, and descriptions of instruments, see the one-volume work:
A great place to begin any music search is to The New Grove Dictionary of Music and Musicians.
Grove's should be your first stop. Articles cover all aspects of music, musicians, composers, historical periods, and so on. Each composer's biography includes a worklist and a bibliography. Be sure to check the bibliography--it can lead you to some new sources.
The online edition of Grove's also contains The New Grove Dictionary of Opera, The New Grove Dictionary of Jazz, and The New Grove Dictionary of American Music.
A print copy of Grove's can be found in the reference section at
REF ML100.N48 2000
Grove's is part of the Oxford Reference collection. Additional titles include: The Encyclopedia of Popular Music, The Oxford Dictionary of Music, and the Oxford Companion to Music.
If you want to search all the sources at once, just type your term(s) in the "Search" box, or you can choose to search only "Grove's" by clicking the box labeled "Search Only Grove Music Online."