There is a later edition (2000 with 29 volumes), but this will do for a while.

Now appearing in print and online simultaneously, this expanded second edition of the most substantial, comprehensive music encyclopedia in English, in 20 substantial volumes, deserves applause for including greater coverage of classical music, nearly 2000 more articles on 20th-century composers, and more than 29,000 entries (many rewritten or revised) by over 6000 contributors nearly 7000 more entries by 3600 more contributors than graced the 20-volume 1980 edition. New articles on intellectual trends (e.g., deconstruction, modernism, and postmodernism), sociopolitical movements (e.g., feminism, Marxism, and Nazism), and even animal music and sex illuminate music's various contexts far better than did the earlier New Grove's. One brave entry's topic is music itself. Only the print version is fully illustrated, and the musical examples are best viewed on the printed page, for only there can users see longer examples in their entirety while reading the accompanying narrative.

from Margriet Tindemans