INTERVAL

in music, is the difference in pitch between two sounds; the ratio between the frequencies (vebrations) of two notes. Intervals are reckoned from the lower note upwards, both notes being included. They are cla ed according to the number of degrees of the stave—i.e., alphabetical letters—included, not according to number of tones or semi-tones contained. Intervals are subdivided into different cla es, according to number of semi-tones contained: fourths, fifths, and octaves are called perfect; seconds, thirds, sixths, and sevenths are called major and minor. A diminished interval is one that contains a semi-tone le than a perfect or a minor interval, while an augmented interval contains a semitone more than a perfect or a major interval.