Opus number

Opus, from the Latin word opus meaning "work", is usually used in the sense of "a work of art".

Some composers' musical pieces are identified by opus numbers which generally run either in order of composition or in order of publication. The usual abbreviation is "Op." "WoO" stands for "Werk ohne Opuszahl" or "work without an opus number" (particularly in the music of Beethoven). "Op. posth." means "opus posthumous" or "work published posthumously"; however, not all composers who had works published after their deaths have these works noted as "Op. posth." publications. Beethoven, for example, continued to generate regular opus numbers after his death, such as the Rage Over a Lost Penny (published as "Op. 129," suggesting a late work, but actually dating from the 1790s). Another example is Felix Mendelssohn, whose last two symphonies (no. 4, the "Italian," and no. 5, the "Reformation") were among many opus numbers brought out by publishers after his early demise.

Certain composers' works, particularly from the baroque and classicist era, when works were less often written specifically for publication, and when publication numbers that do exist are either inconsistent and/or unhelpful (two opus 1 sets of violin sonatas for Mozart, for instance), have been definitively cataloged by a given scholar, and in such instances these works can be unambiguously referred to by their thematic catalog abbreviations.

The works of Karl Friedrich Abel, while usually referenced by their original publication opus numbers (for example, his Op. 17 symphonies), also have catalog numbers assigned to them by Walter Knape in his Bibliographisch-thematisches Verzeichnis der Kompositionen von Karl Friedrich Abel (Cuxhaven: W. Knape, 1972).
Carl Philipp Emanuel Bach's works have two numbering systems: the older Wotquenne numbering (abbreviated as Wq.) devised by Alfred Wotquenne in his catalog of Emanuel's music published in 1905, and the more complete and up-to-date numbering by E. Eugene Helm (abbreviated as H.), as presented in Helm's Thematic Catalogue of the Works of C.P.E. Bach (New Haven: Yale University Press, 1989).
Johann Christian Bach's works are most often referred to by the opus numbers assigned by their original publishers, which can cause identification difficulties because different publishers used the same opus number. (For instance, "Op. 18" was used for three different sets of J.C. Bach works: "Six Grand Overtures," "Deux sinfonies," and "Four Sonatas and Two Duets.") Because of this, some have used C.S. Terry's John Christian Bach (2nd edition; London: Oxford University Press, 1967) as the basis for a de facto standard, using the page number and incipit number in Terry for identification even though these numbers were not assigned by Terry for cataloguing purposes. (For a convenient short listing of these numbers, see Christoph Wolff, et al., The New Grove Bach Family [NY: Norton, 1983], pp. 341ff..) Numbers are also sometimes used from the Thematic Catalog in the Collected Works of Johann Christian Bach (gen. ed. Ernest Warburton; NY: Garland Publishing, 1985).
Johann Sebastian Bach's works are referred to by their BWV or Bach-Werke-Verzeichnis numbers after the catalogue by Wolfgang Schmieder.
Wilhelm Friedemann Bach's works were catalogued by Martin Falck in 1913, and are often referred to by their F (or Falck) numbers.
Marc Antoine Charpentier's works are referred to by the H or Hitchcock numbers after Hugh Wiley Hitchcock.
George Frideric Handel's works are often designated by HWV (Händel-Werke-Verzeichnis) numbers as given in the Verzeichnis der Werke Georg Friedrich Händels by Bernd Baselt. (See this page at gfhandel.org for additional details.)
Joseph Haydn's works are referred to by their Hob or Hoboken numbers after Anthony van Hoboken's 1957 classification.
Franz Liszt's works are referred to by their S or Searle numbers after Humphrey Searle's 1960s classification The Music of Liszt. Alternately, R is used to refer to Peter Raabe's 1931 reference Franz Liszt: Leben und Schaffen.
Wolfgang Amadeus Mozart's works are referred to by their K or Köchel numbers, after Ludwig von Köchel. In continental Europe, the German abbreviation "KV" for Köchel-Verzeichnis is more common. See also: List of compositions by Wolfgang Amadeus Mozart
Antonio Rosetti's works are usually given with catalog numbers by Sterling E. Murray, Chairman of the Department of Music History at West Chester University of Pennsylvania,[1] although older numbers from Oskar Kaul's 1912 Rosetti catalog sometimes appear as well. For example, Rosetti's popular "La Chasse" symphony is numbered as "Murray A20/Kaul I:18."
Domenico Scarlatti's harpsichord works have two numbering systems: the L or Longo numbers after Alessandro Longo's edition for piano, and the K or Kirkpatrick numbers after Ralph Kirkpatrick's facsimile edition.
Franz Schubert's works are referred to by their D or Deutsch numbers after Otto Erich Deutsch's catalogue.
Antonio Soler's keyboard sonatas are usually referred to by their R number, after the catalogue compiled by Father Samuel Rubio.
Antonio Vivaldi's works are referred to by their RV or Ryom-Verzeichnis numbers after Peter Ryom's catalogue.
Richard Wagner's works are referred to by their WWV or Wagner-Werke-Verzeichnis numbers, which also include his non-musical work.

See also