The Neapolitan chord (N) is a major triad built on the lowered second scale degree ( II ⁵ ).

The chord is available both in major and minor keys. It is a prolongation or substitute of the predominant area.The chord is most often found in first inversion and is called the Neapolitan sixth chord (N⁶). The name probably originated in Italy during the Baroque era.

The Neapolitan chord as a substitute for the supertonic chord in major (ii) and minor (ii^o):

The Neapolitan chord is more frequently used in minor keys. In minor keys, the ii^o triad becomes II5.

In major keys, the Neapolitan chord contains ra (the lowered 2^nd scale degree) and le (the modally borrowed 6^th scale degree).

As with IV and ii⁽⁶⁾, the bass (the 3^rd of the chord) is doubled in the N⁶ chord. Between N⁶ and the dominant (N⁶ – V) or dominant group (N⁶ – [i] – V), the upper voices move in contrary motion against the bass. Due to the contrary motion, ra moves down to ti, creating a double leading tone effect moving to the tonic: ra – ti – do.

Voice Leading

The N and N⁶ chords are often preceded by the i⁽⁶⁾, iv, or VI chords in harmonic minor and the I⁽⁶⁾, iv, or VI chords in major. In example #4, the movement of VI to the root position N triad is a falling 5^th connection, with the VI chord acting as the dominant of the Neapolitan chord.

Example #5 is written in la-minor. The lowered 2^nd scale degree is te.

In minor keys, the movement of VI to the root position N triad is a falling 5^th connection (example #6).

In the diatonic sequence in minor (example #7), the Neapolitan triad replaces the ii^o triad. The example is written in la-minor, with the lowered 2^nd scale degree being te.

The Neapolitan Chord in Modulation

1. Using the Neapolitan chord to modulate

The chart below illustrates the use of the Neapolitan chord as a modulating device to distant keys from C major or C minor.

For example:

The Neapolitan chord may be employed at times enharmonically. For example, in the modulation from C major to F-sharp minor, D/F is enharmonically reinterpreted as C/E.

2. Doubling when using N⁶ to modulate

It is not possible to double the N⁶ (II⁶) chord properly in both the departure and arrival keys. Use common sense to decide which solution is more practical, but do not double the bass (3^rd of the chord) if it is the leading tone in the new key. In the example below, the N⁶ is not doubled correctly in D major, but it is doubled correctly as V⁶ in A-flat major.