This work is not one of the usual harmony theories, but rather an attempt to systematically justify the most important areas of music theory (harmony and tonality). The results are a new, more precise definition of harmonic designation (narrowest form) and the objectification of harmonic analysis through the separation of designation and interpretation of a chord. The consistently executed theory of tonality and the determination of the actual key enable an analysis that becomes comparable for all eras and styles for the first time.