What Are Octaves? An octave is a musical interval spanning eight diatonic scale degrees. In simpler terms, it’s the distance between a musical note and another note with double or half its frequency. This interval is fundamental in music theory and often forms the basis of harmony and melodies. On the guitar, octaves are useful for creating harmony, adding depth to chords, and playing melodies. Players often use octaves to expand the range of a melody or to create a fuller sound when playing cho