This is a quick reference guide to the cataloging systems employed in order to organize works.
A huge collection of cataloging systems can be found here.
The title of a composition is generally followed by cataloging information, such as "Op.8, K.145". These are added by composers, editors, and publishers to identify a composition (usually chronologically) by a composer. Generally speaking, a higher cataloging number means the work was composed later, but exceptions do occur. One example is when the cataloging number denotes order of publication.
Bach Werke Verzeichnis (Bach Works Catalog), is a method of cataloging the works of Johann Sebastian Bach. It was established by the Thematisch-systematis-ches Verzeichnis der musikalischen Werke von Johann Sebastian Bach, by Wolfgang Schmieder in 1950. Occasionally S. is used to denote Bach's works.
This is used in relation to the works of Franz Schubert. It was established by Otto Erich Deutsch.
This is a system for identifying the works of Carl Philipp Emanuel Bach from a catalog by E. Eugene Helm issued in 1989 (see also Wq.)
This is used in relation to the works of Franz Joseph Haydn. It stands to Hoboken, and was first employed in Anthony van Hoboken's Thematisc-bibliographisches Werkverzeichnis.
This is the system used for identifying the works of George Frideric Handel. Händel-Werke-Verzeichnis numbers were allocated by Bernd Baselt.
This is used in relation to the works of Wolfgang Amadeus Mozart. Kochel is a cataloging system used in Ludwig Kochel's Chronologisch-thematisches Vereichnis, published in 1964.
This is used for identifying the sonatas of Domenico Scarlatti. It was first used in Alessandro Longo's collection of Scarlatti's sonatas. It is also employed for François Lesure's catalog of Debussy's works.
Opus (latin, work), is the most common cataloging system. Several compositions of the same type are often shared with the same Opus number (e.g. "Op.7, No.2"). The plural is Opp.
This system is used for identifying the keyboard sonatas of Soler, Antonio. These were established after the catalogue compiled by Father Samuel Rubio.
This is the system used to identify the works of Antonio Vivaldi. Ryom-Verzeichnis numbers are used for Peter Ryom's catalogue. Some of Vivaldi's works were published as opus sets, and these numbers are sometimes used as well.
This is a system used for identifying the works of Béla Bartók. It was employed by András Szőllősy.
This system is also used to classify the works of Villa-Lobos, without a period after "W".
This is a system for identifying the works of Carl Philipp Emanuel Bach from a catalog by Alfred Wotquenne issued in 1905 (see also H.).
This is a system for identifying the works of Richard Wagner. Wagner-Werke-Verzeichnis numbers also include his non-musical works.