Jean-Philippe Rameau · section 17 of 109

CHAPTER THREE. On the Nature and Properties of the Octave

The octave, which contains all the sounds that can together compose fundamental chords, may be added to them to increase their perfection. Without it, the perfect chord and its derivatives still exist; with it, they become more brilliant, because the natural and inverted chords sound simultaneously. In four-part pieces its use is indispensable, and in five-part pieces it agrees perfectly with the sounds of the fundamental seventh chord. In short, it may always be joined to chords containing only one minor dissonance. Its progression, which must be diatonic in the upper parts, readily obeys the rules. Moreover, it determines modulation, as we shall see later.