Opus number developed other catalogue-number systems; among them the "Bach-Werke-Verzeichnis" (BWV-number), and the "Köchel-Verzeichnis" (K- and KV -numbers) with which are organised the works of Johann Sebastian Bach and Wolfgang Amadeus Mozart, respectively. In the classical period, the Latin word "opus" ("work", "labour") was used to identify, list, and catalogue a work of art. By the 15th and 16th centuries, the word "opus" was used by Italian composers to denote a specific musical composition, and by German composers for collections of music. In compositional practise, numbering musical works in chronological order dates from 17th century Italy, especially Venice. In common usage, the
Catalogues of classical compositions For example, Liszt's works are now known only by S numbers, from the catalogue by Humphrey Searle, which superseded that created by Peter Raabe, which used R numbers. Older catalogues are included for historiographic purposes. But there are exceptions to this, such as: The following incomplete list gives details of many of the catalogues and symbols that have been used, and in many cases are still in use. It is in author or composer order, but can be sorted in symbol order. Catalogues of classical compositions This article gives some details of the various catalogues of classical compositions that have