Kirchmeyer catalog numbers provide a helpful shorthand to refer to Strawinsky’s works. Opus numbers are assigned by composers to their compositions, Opus numbers often are incomplete and only roughly indicate a chronological order. Opus numbers have been used inconsistently throughout history, and in case of Strawinsky the amount of variations and derivations of his works require a different system to organize a catalog. Several attempts have been made before Kirchmeyer came up with his annotated catalog that is now widely accepted.