MODE, in Music, a regular disposition of the air and accompaniments, relative to certain principal sounds upon which a piece of music is formed, and which are called the essential sounds of the mode.
Our modes are not, like those of the ancients, characterized by any sentiment which they tend to excite, but result from our system of harmony alone. The sounds essential to the mode are in number three, and form together one perfect chord. 1. The tonic or key, which is the fundamental note both of the tone and of the mode. 2. The dominant, which is a fifth from the tonic. 3. The mediant, which properly constitutes the mode, and which is a third from the same tonic. As this third may be of two kinds, there are of consequence two different modes. When the mediant forms a greater third with the tonic, the mode is major; when the third is lesser, it is minor. See MUSIC.