Encyclopedias and dictionaries are the best places to gain a basic understanding of your topic, and those on music give information about composers, musical works, instruments, genres of music, and musical terms.
Make it a habit to explore your topic using these resources when starting the learning process.
Encyclopedias and dictionaries are available in both electronic and print formats, and can be either general in subject coverage or subject specific.
Oxford Music Online includes:
Grove Music Online is the leading online resource for music research ... offering the full texts of The New Grove Dictionary of Music and Musicians, 2nd edition (2001), The New Grove Dictionary of Opera (1992), and The New Grove Dictionary of Jazz, 2nd edition (2002), as well as numerous subsequent updates and emendations... Grove Music Online is the unsurpassed authority on all aspects of music.
The Oxford Companion to Music (2002) and The Oxford Dictionary of Music, 2nd edition (revised 2006),supplement Grove's more-extensive coverage with content geared toward undergraduates and general users.