What is Neapolitan 6th chord? Neapolitan 6th chord (often abbreviated as N6) is a major chord built on the lowered second degree (supertonic) of a major or minor diatonic scale. It is the same whether in major or minor key. Neapolitan is the language of Naples, Italy. At this point, it suffices to say that the chord is originated from Italy.
First of all, you must know how to build N6 chord. First, locate the supertonic; reduce it by a semitone, construction a major triad on it. Place it on it 1st inversion. Using the above outline, let’s find the Neapolitan 6th chord of the following keys: C major, Bb major, G major and Eb major
Neapolitan 6th chord of key C Major: C D E F G A B CI is the C major scale. D is the second scale degree (supertonic). To reduce it by a semitone, you turn it to Db. If you build a major triad on it, you’ll have Db F Ab. Its first inversion will be F Ab Db. Therefore, the N6 of chord of C is F Ab Db.
Neapolitan 6th chord of key Bb Major: The second scale degree is C. If you reduce it by a semitone, you’ll have Cb. If you build a major triad on Cb, you’ll have Cb Eb Gb. If you place the constructed chord in its first inversion, you’ll have Eb Gb Cb. Therefore, the N6 of key Bb major is Eb Gb Cb.
Neapolitan 6th chord of key G Major: The second scale degree is A. If you reduce it by a semitone, you’ll have Ab. If you build a major triad on Ab, you’ll have Ab C Eb. If you place it in its first inversion, you’ll have C Eb Ab. Therefore, the N6 of key G major is C Eb and Ab.
Neapolitan 6th chord of key Eb Major: The second scale degree is F. If you reduce it by a semitone, you’ll have Fb. If you build a major triad on Fb, you’ll have Fb Ab Cb. If you place the built chord in its first inversion, you’ll have Ab Cb Fb. Therefore, the N6 of the key of Eb major is Ab Cb and Fb.
Worthy of note is the function of Neapolitan 6th Chord. In harmony, the function of N6 chord is to anticipate or prepare the dominant. It leads to the dominant. It can be used in place of the supertonic and subdominant triads. That is, N6 is a substitute for chords ii and IV.
Notice that the N6 has the same bass note (lowest note) with the root position of subdominant chord and the 1st inversion of the supertonic chord. For these reasons, it’s often substituted for these chords.
Neapolitan 6th chord (when not inverted) is symbolized by capital letter N or bii. It’s not usually used in root position. It’s always used in 1st inversion; that’s why it called Neapolitan 6th chord.
It can be inverted; the 1st inversion is seen as N6 or bii6. Chord I of F major is the N6 chord of E major. Chord I of A major is the N6 of Ab. It’s usually used in its 1st inversion.
The resolution of the N6 Chord is of great importance. The lowest note (the 3rd) of the N6, if it’s in the bass resolves upward, one whole step to the root of the dominant chord. If it’s in the soprano or any other voice, it can resolve downward, a minor 3 to the 5th of the dominant.
The 5th usually resolves downward, a semitone to the root of the dominant (V). The root can either resolve downward, a whole step to the 3rd of the dominant or upward, a half step to the 5th of the dominant (V).
For more, read Tonal Harmony: Learning Principles/Prerequisites, The concept of Scale, The Concept of Triad, The Concept of Seventh Chord, The Characteristics and Resolutions of Secondary Dominant Chords, Augmented Sixth Chords.