Check Scholar for more specific reference books, such as lists of music for specific instruments, biographies of composers, history and criticism of musical periods, etc.
This subscription to Grove Music Online includes access to Oxford music reference titles, including The Oxford Companion to Music, The Encyclopedia of Popular Music and The Oxford Dictionary of Music.
This series takes a cultural approach to its focus on the music of all the world's peoples. Each volume is arranged topically, regionally, or by ethnic group, and complemented by an extensive index and audio CD.