Jean-Philippe Rameau · section 36 of 109

Chapter twenty-two

The source of our freedom to pass from one mode or key to another

The consonant progression of a fundamental bass, over which only perfect chords are sounded, offers us as many different keys as there can be different sounds in that bass. For since the perfect chord alone belongs specifically to a tonic note, the key is always established upon each of these notes. Thus, from the consonances received from the first divisions of the string, we derive not only all chords, all melody, and the manner of proceeding within one key, but also the manner of passing from one key to another, as we explain in Book III. We need not trouble ourselves whether the key should be major or minor, since we are always governed by the one we are leaving. Notice that here we include the term mode within the term key when the difference between major and minor is not heard upon the same tonic note. For we can change the mode from major to minor, or minor to major, without changing that mode's tonic or principal note. For example, when a cheerful subject gives way to a sad one, or a sad one to a cheerful one—as occurs in most chaconnes or passacaglias, and often in two successive airs of the same kind—we may say that the key does not change although the mode changes. For if C is the tonic in the major mode, it is also the tonic in the minor. To avoid confusing the terms, we simply say major key and minor key. With regard to melodic and harmonic movement, the key can change only from major to minor or from minor to major. With regard to the tonic note, however, it can be taken on the twenty-four different notes of the chromatic system, though not indiscriminately during a piece. For although we may choose whichever note we please for the beginning and ending, we can leave it only to pass to another related to it or to the notes of its chord. By such a chain of connections, we are obliged to return when it is time to conclude and finish.