‹‹‹ Vitr. 5.4.2 | Table of Contents | Vitr. 5.4.4 ›››
3There are three sorts of modulation, the enharmonic (ἁρμονία), the chromatic (χρῶμα), and the diatonic (διάτονος), so called by the Greeks. The enharmonic is so constructed by art, as to be full of majesty and pathos. The chromatic by the skilful contrivance and closeness of its intervals has more sweetness. The diatonic, whose intervals are more simple, is most natural. The disposition of the tetrachords, in these genera, are dissimilar. The enharmonic tetrachord consists of two dieses, and two whole tones; a diesis being the fourth part of a tone, and two of them consequently equal to a semitone. In the chromatic tetrachord, there are two consecutive semitones, and the third interval contains three semitones. The diatonic tetrachord has two consecutive tones, and an interval of a semitone. Thus in each genus, the whole tetrachord is equal to two whole tones and a semitone. But the intervals in each genus, differ when considered separately.
3There are three classes of modes: first, that which the Greeks term the enharmonic; second, the chromatic; third, the diatonic. The enharmonic mode is an artistic conception, and therefore execution in it has a specially severe dignity and distinction. The chromatic, with its delicate subtlety and with the “crowding” of its notes, gives a sweeter kind of pleasure. In the diatonic, the distance between the intervals is easier to understand, because it is natural. These three classes differ in their arrangement of the tetrachord. In the enharmonic, the tetrachord consists of two tones and two “dieses.” A diesis is a quarter tone; hence in a semitone there are included two dieses. In the chromatic there are two semitones arranged in succession, and the third interval is a tone and a half. In the diatonic, there are two consecutive tones, and the third interval of a semitone completes the tetrachord. Hence, in the three classes, the tetrachords are equally composed of two tones and a semitone, but when they are regarded separately according to the terms of each class, they differ in the arrangement of their intervals.