Diatonic

Diatonic (from the Greek) means 'by tones,' or 'from tone to tone.' The diatonic species of the ancient Greeks—as distinguished from their chromatic and enharmonic species—formed the foundation of their whole system of music, and was arranged in tetrachords (embryo seales) composed of one semitone and two whole tones. In modern music, the term is applied to (1) the natural or normal scale, major or minor, which proceeds mainly by whole tones; (2) the different species of intervals (usually reckoned as fourteen in number) occurring between the various notes of that scale; and (3) music written wholly or for the most part in that scale.