in Music, (compounded of two Greek words, viz. the preposition δια, signifying a transition from one thing to another, and the substantive τονις, importing a given degree of tension or musical note), is indifferently applied to a scale or gamut, to intervals of a certain kind, or to a species of music, whether in melody or harmony, composed of these intervals. Thus we say the diatonick series, a diatonick interval, diatonick melody or harmony. As the diatonic scale forms the system of diatonic music, and consists of diatonic intervals, it will be necessary, for understanding the former, that we should explain the latter. See INTERVAL.