"Grove" originated as a print dictionary (encyclopedia really) and has been published since 1878 in many editions. In 2001 it was launched as an online publication.

In English. "The first stop for music research." Includes subjects and biographies and is arranged alphabetically. The online version is updated periodically. 

Both print and online versions include:

• extensive bibliographies
• lists of composers works ("works lists')

Print versions:

[Mus Ref Book ML100 .N48]

The New Grove dictionary of music and musicians. 2nd edition. London : Macmillan Publishers ; Washington, D.C. : Grove's Dictionaries of Music, 2001.

29 volumes. Most recent physical edition. Edited by Stanley Sadie.

[Mus Ref Book ML102.I5 N48 2014]

The Grove dictionary of musical instruments. 2nd edition.  New York : Oxford University Press, [2014]

5 volumes. Most recent physical edition. Edited by Laurence Libin.

Online version: Grove Music Online

Includes:

• The New Grove Dictionary of Music and Musicians, 2nd edition (29 volumes, 2001)
• The New Grove Dictionary of Jazz, 2nd edition (3 volumes, 2002)
• The New Grove Dictionary of Opera (4 volumes, 1992)
• The Norton Grove Dictionary of Women Composers (1 volume, 1994)
• The Grove Dictionary of American Music, 2nd edition (8 volumes, 2013; in process)
• The Grove Dictionary of Musical Instruments, 2nd edition (5 volumes, 2014; in process)

Examples:

Subjects: Mechanical Instrument   Player piano   Carillon   Midi   Music box

Theremin

Biographical: Thomas Edison   Moog, Robert   Schaeffer, Pierre   Buchla, Donald 

Oxford Music Online. Oxford University Press purchased Grove Music Online and created a comprehensive site that includes all of the above titles as well as other online resources from Oxford University Press.  Determining the source of the article could be useful to you in identifying the article's focus (for example if the article is from the The Grove Dictionary of American Music the article will discuss the person/item in America or from an American perspective.) You can tell the where any of the Grove title articles originate by examining the "DOI" address: there will be an  "A" before the final number in the DOI address for an article from The Grove Dictionary of American Music. Example:  Carillon.