OCTAVE

in music, an interval whose higher note has a sound-wave frequency of vibration double that of its lower note. Thus, the note a vibrates at 220 hertz [cycles per second], while its octave, a, vibrates at 440 hertz. Because of the close acoustical relation between the two notes, the second is perceived by the listener as identical with the first at a higher pitch. The octave encompasses a variety of musical scales, including the church modes and major and minor scales of Western music. The octave encompasses eight notes of a scale in Western music. It is the only interval to appear as a constant in the musical scales of nearly every culture.