With the founding of the Paris Conservatory in 1795, a diversity of instructional methods for the teaching of harmony were used. Each theory instructor insisted upon using his own system; some relied heavily upon the theories of Rameau, while others used ideas based on eighteenth century German or Italian theorists. The Conservatory administration, realizing the need to unify theoretical instruction into a single method, formed a committee to evaluate the different harmonic systems available. After considering several treatises, including the theories of Rameau, the committee chose the Traité d'harmonie of Catel as the work best suited for their purposes. This investigation deals with Catel's synthesis of various theoretical principles, concentrating on his concise, often simplistic approach to harmonic theory. The major contribution of the Traité is the classification of chords into two categories: "natural harmony" and "artificial harmony." Catel believed that only one chord exists in harmony, the dominant ninth chord, which he derived from the first nine partials of the overtone series. From this chord, he formed the basic triads of "natural harmony," describing these chords as suspensions ("prolongations") of "natural harmony."