Abacus Harmonicus, or Abacum Arithmetico-Harmonicum is a table and tabular method described in Athanasius Kircher's comprehensive 1650 work on music, the Musurgia Vniversalis.^[1] The purpose is to generate counterpoint combinations. Also mentioned in early editions of the Encyclopædia Britannica, it is best described by the author's caption: "wonderful table that reveals all the secret art of counterpoint".