Neapolitan, augmented sixths, chromatic mediants
Music theory · Tonal harmony · Level 6 · 18 min
Three rarer harmonic colours that make all the difference in Mozart, Beethoven, Schubert, Chopin… and film music. All of them rely on chromaticism.
1. The Neapolitan sixth (N6 or ♭II6)
This is the major chord built on the lowered 2nd degree, almost always in first inversion. In C minor: D♭ major (D♭–F–A♭), with F in the bass. It acts as a predominant and leads to V. The D♭ falls to B♮ (the leading tone), sometimes passing through C: a very expressive diminished-third motion.
M:4/4
L:1/4
%%staves {RH LH}
V:RH clef=treble
V:LH clef=bass
K:Cm
[V:RH] "Cm"[EGc]2 "Db/F"[FA_d]2 | "G7"[FG=B]2 "Cm"[EGc]2 |]
[V:LH] "_i"C,2 "_N6"F,2 | "_V7"G,,2 "_i"C,2 |]
You hear it in the first movement of Beethoven's “Moonlight” Sonata and in countless minor-key pieces: it's the sound of pathos.
2. Augmented sixth chords
They are built on an augmented sixth between the lowered 6th degree in the bass (A♭ in C) and the raised 4th degree (F♯). The two notes each move outward by a semitone to the octave on the dominant, G. There are three kinds, named after purely conventional “nationalities”:
| Name | Notes (going to G) | Note |
|---|---|---|
| Italian (It+6) | A♭ – C – F♯ | three notes, the lightest |
| French (Fr+6) | A♭ – C – D – F♯ | an extra tritone, a “whole-tone” colour |
| German (Ger+6) | A♭ – C – E♭ – F♯ | sounds exactly like A♭7 |
M:4/4
L:1/4
%%staves {RH LH}
V:RH clef=treble
V:LH clef=bass
K:Cm
[V:RH] "^It+6"[c^f]2 [=Bg]2 | "^Ger+6"[c_e^f]2 [ceg]2 | [=Bdg]2 [ceg]2 |]
[V:LH] _A,,2 G,,2 | _A,,2 G,,2 | G,,2 C,2 |]
Bar 1: Italian sixth → V. Bars 2-3: German sixth → cadential six-four → V → i (going through the 6/4 avoids the parallel fifths A♭–E♭ → G–D).
The German sixth sounds like a dominant seventh (A♭7): that's its secret kinship with jazz's tritone substitution (A♭7 → G).
3. Chromatic mediants
Two chords of the same quality (two major chords, say) whose roots are a third apart and which share just one common tone: C → E, C → A♭, C → A, C → E♭. They have no functional relationship, yet the progression has a magical effect, luminous or unsettling. Schubert, Liszt and Wagner loved them; film music made them its signature (outer space, the marvellous).
M:4/4
L:1/4
%%staves {RH LH}
V:RH clef=treble
V:LH clef=bass
K:C
[V:RH] "C"[EGc]2 "E"[E^GB]2 | "C"[EGc]2 "Ab"[_E_Ac]2 | "C"[EGc]4 |]
[V:LH] C,2 E,2 | C,2 _A,,2 | C,4 |]