DIATONIC, in Music, a word compounded of the Greek proposition dia, signifying transition, and tonos, tension, is indifferently applied to a scale or gammut, 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 diatonic series, a diatonic interval, diatonic melody or harmony. The diatonic scale forms the system of diatonic music, and consists of diatonic intervals.