A sixth is the interval embracing six diatonic degrees. It can also mean the tone at this interval (i.e., the submediant), and the harmonic combination of two tones a sixth apart.

 

A sixth encompasses six staff positions, and occurs most commonly in two forms – the major sixth (spanning nine half tones) and the minor sixth (spanning eight half tones). For example, the interval from C to A is a major sixth, as the note A lies nine half tones above C, and there are six staff positions from C to A. A major sixth is an inverted (see inversion) minor third (and vice versa), and the minor sixth is an inverted major sixth. Diminished and augmented sixths span the same number of staff positions, but consist of a different number of half tones (seven and ten). A commonly cited example of a melody featuring the major sixth as its opening is "My Bonnie Lies Over the Ocean."

 

An added sixth is a chord made up of a tonic triad (root, third, and fifth) with the sixth added, e.g. CEGA. It is used frequently in jazz and popular music.

 

A Neapolitan sixth is a chord constructed on the fourth degree of a diatonic scale with a minor third and a minor sixth above the bass.