Köchel catalogue
The Köchel catalogue (German: Köchel-Verzeichnis) is a catalogue of compositions by Wolfgang Amadeus Mozart, originally created by Ludwig Ritter von Köchel, in which the entries are abbreviated K. or KV. Its numbers reflect the ongoing task of compiling the chronology of Mozart's works, and provide a shorthand reference to the compositions. For example, according to Köchel's counting, Requiem in D minor is the 626th piece Mozart composed, thus is designated K. 626.
Köchel's original catalogue (1862) has been revised several times. Catalogue numbers from these revised editions are indicated either by parentheses or by superscript: K. 49 (47d) or K.6 47d refers to the work numbered 47d in the sixth edition. The catalog was originally chronological, though revisions made chronological ordering of Mozart's works difficult and as of 2024 a new organizational system is used for the ninth version.