Answered By: Information Commons Last Updated: Jul 01, 2014 Views: 97
Some composers' musical works are identified by opus numbers. Publishers often assign these numbers to a given composer's works by order of their composition or order of their publication. The usual abbreviation is "Op.". Occasionally, one also may see the designation, "WoO," which stands for "Werk ohne Opus" or "work without an opus number" or "Op. posth." which means "opus posthumus" or a work published after the composer's death.
- Berlioz's Les nuits d'été, Op. 7