[84] for the breath being sent from the dominant part of us through the artery called the trachea, is formed in the mouth by the tongue, as by a kind of workman, and being borne outward, and mingled with its kindred air, and having struck it thus harmoniously, completes the mixture of the two [36] powers; for that which sounds together by a combination of different noises is at first adapted to a divisible duad, having one sharp and one flat tone: