In music, an octave ('s the interval between one musical pitch and another with half or double its frequency. The octave "relationship's a natural phenomenon which has been referred to as the 'basic miracle of music,'" the use of which's "common in most musical systems."(Cooper 1973, p.16) The octave's occasionally referred to as a diapason. The octave above an indicated note's sometimes abbreviated 8va, and the octave below 8vb. To emphasize that it's one of the perfect intervals, the octave'… (More on Octave)