Oxford Music Online covers the history of music and its genres up to the present; it contains more than 80,000 articles, images, musical notations, and music samples, more than 20,000 biographies of composers, interpreters, and writers whose works have been set to music. It offers full-text search of articles in the following resources:

• Grove Music Online (The New Grove Dictionary of Music and Musicians, The New Grove Dictionary of Opera and The New Grove Dictionary of Jazz) – includes nearly 60,000 terms, 30,000 biographies, more than 20,000 subject headings, and more than 5,000 images.
• The Oxford Dictionary of Music – a collection of nearly 12,000 subject words has been compiled by internationally renowned specialists in all areas of music. The articles deal with opera, ballet, orchestras, music groups or concert halls. This encyclopedia also deals with ancient music and non-traditional instruments used at that time.
• The Oxford Companion to Music – this large publication maps the musical styles from the Middle Ages to the present day. Nearly 8,000 articles deal with composers, performers, writings, instruments, and musical notations, making this resource unique in this field.

You can see a sample of uses here.