‹‹‹ Vitr. 5.4.8 | Table of Contents | Vitr. 5.5.1 ›››
9For between two intervals, either in a melody sung by a voice, or played on a stringed instrument, neither with the third, sixth nor seventh can there be consonances, but only, as above shewn, with the diatessarôn and diapente up to the diapasôn do natural consonances arise, and those are produced by an union of those sounds which the Greeks call φθόγγοι (phthongi).
9For there can be no consonancies either in the case of the notes of stringed instruments or of the singing voice, between two intervals or between three or six or seven; but, as written above, it is only the harmonies of the fourth, the fifth, and so on up to the double octave, that have boundaries naturally corresponding to those of the voice: and these concords are produced by the union of the notes.