Neapolitan and Augmented 6th Chords

Chromatic Harmony Neapolitan and Augmented 6th Chords

Altered Pre-Dominant Chords

This family of vertical sonorities includes all types of chromatically altered chords that precede the dominant (V) function in tonal music. They typically progress to the dominant, but may be used in other progressions or retrogressions. A borrowed subdominant minor chord followed by the dominant harmony in a major key is technically an altered pre-dominant chord. A secondary dominant, or V/V, would also qualify. But most often the term refers to Neapolitan and Augmented 6^th chords.

The Neapolitan Chord

This chord is simply a major triad built on the lowered second scale degree. It is typically found in a minor key, usually in first inversion. It is analyzed with the symbol “N”, or “N⁶”. It may also be identified as “♭II”, or “flat two.” It has a striking effect aurally, and is quite a jolt when used in a major key, with both the 2^nd and 6^th lowered at once. An easy way to spell this triad is to begin with a minor subdominant chord. The 5^th of the iv chord is the tonic of the key, and you can create a Neapolitan sixth by replacing the tonic with the lowered 2^nd scale degree. This process puts it in first inversion.

The name is derived from 18^th century opera composers working in the area of Naples. They did not invent the chord, but the term Neapolitan and the abbreviation stuck.

Voice-Leading Neapolitan Chords

In four-part Baroque and Classical period music, the third of the N⁶ chord in the bass was doubled. The root, an altered 2^nd scale degree, is frequently found in the soprano voice. It resolves downward to the leading tone when followed by the V chord. This creates the interval of an augmented 2^nd, which is normally avoided in traditional part writing. It resolves by half-step to the tonic when followed by the tonic chord in second inversion, or to the V chord in third inversion. As in most voice-leading situations, lowered scale degrees generally resolve downward. A lowered 2^nd scale degree is the clue to analyzing this chord.

The Augmented 6^th Chord

There are three common varieties of this chord, but they all share several characteristics. All three most often function as a pre-dominant chord. Here is a simple way to identify or create the augmented sixth interval:

It is a linear approach to the doubled fifth scale degree by half-step, in contrary motion.

This chord is most often found in a minor key, in which the diatonic minor 6^th scale degree is the bass note. The #4 scale degree of the key is added to create the augmented 6^th interval, which is an enharmonically spelled m7^th above the bass. The raised 4^th is the best clue to identifying any augmented sixth chord. Other chromatic triads with the #4 are V/V and V/iii in major keys, and vii^o/V in major or minor keys. However, these will not contain a minor 6^th scale degree.

To create an Italian, German, or French augmented sixth chord in four voices, add the notes specified below to the augmented sixth interval.

It+6 – Add the tonic pitch of the key, which is doubled. (le, do, fi)

Fr+6 – Add the tonic pitch and the 2^nd scale degree of the key. (le, do, fi, re)

Ger+6 – Add the tonic pitch and the minor 3^rd of the key. (le, do, fi, me)

The Ger+6 is enharmonically equivalent to a Mm7^th chord built on the minor 6^th scale degree. Take away the 5^th of the Mm7^th chord and it becomes an It+6, which has just three notes. Lower the 5^th of the Mm7^thchord, spelled as a #4^th,and you have a Fr+6 chord.

Voice-Leading Augmented 6^th Chords

When voice-leading the augmented sixth chords, resolve each tone according to its tendency. The minor 6^th and raised 4^th resolve outwards, and common tones are retained. When the Ger+6 resolves to the tonic 6/4, two common tones are present between the chords. When resolving the Fr+6 chord to V, the 2^nd scale degree is a common tone with the fifth of the dominant chord. These augmented sixth chords are best seen as linear constructs, rather than vertical harmonies in inversion. Some theorists in the past have analyzed the It+6 with the Roman Numeral ♯iv⁶, but this practice is not common.

When used in major modes, the minor 3^rd of the Ger+6 may be enharmonically respelled as #2, which resolves upwards to ♮3. Spelled this way, it is referred to as a doubly-augmented sixth chord. The Ger+6 is enharmonically equivalent to the V7/N, a secondary dominant to the Neapolitan chord. In the key of C, this provides a convenient pivot chord for a chromatic modulation to D♭. In Jazz applications, the Ger+6 is commonly used as a tritone substitute for the secondary dominant of V. In the key of C, the tritone of V7/V is C-F#, which is enharmonically spelled as C-G♭.