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===== French ===== R M3 P5 a6 -M3- -m3- -M3 ----tt---- ----P5---- -------a6------- The German 6th is enharmonically equivalent to a dominant 7th chord. The difference is its usage, functioning as a sub-dominant for the given key rather than the dominant for the {{b}}II key. The added P5 here makes for difficult voice leading, often requiring to move it before or to resort to inverting the subsequent dominant chord.
→Augmented Sixth Chords
== Chromatic Chords ==
=== Augmented Sixth Chords ===
''Augmented sixth'' chords are named for the augmented 6th interval they contain. An a6 is enharmonically equivalent to a m7 interval; however, it is spelled as an a6 here for its relation to the surrounding key and its harmonic usage. The a6 occurs between the m6 and a4 notes of the key. The chords take a sub-dominant harmonic function, and when resolving to v or V, the m6 resolves down a half-step while the a4 resolves up a half-step to form an octave of the P5 of the key's tonic note.
If that was confusing hopefully this example helps: In C Major, an augmented sixth chord will feature A{{f}} and F{{s}} (the distance from A{{f}} to F{{s}} is 11 semitones or an a6 interval). To move to the dominant or V chord (G), A{{f}} descends to G and F{{s}} ascends to G, increasing the distance to 13 semitones or 1 octave.
There are 3 variations of the augmented sixth:
===== Italian =====
The ''Italian 6th'' (It+6 or It6) features the m6, U, and a4 notes from the current key. In other words, it is comprised of root, M3, and a6.
R M3 a6
-M3- -tt-
----a6----
If the chord contained the P5 of the root, it would be enharmonically equivalent to a dominant 7th chord, built upon the {{f}}VI note of the scale. Yet it does not function harmonically as such. Its M3 does not function as a leading tone, and it does not resolve to the {{f}}II chord. Rather the M3 moves down a half-step to become the leading tone for the V chord or up a whole step to be the 5th of the V or v chord. In 4-part writing, the M3 is doubled and each resolves in contrary directions to form the 3rd and 5th of the V chord, while the R and a6 move contrary to both become the root of the V.
===== French =====
The ''French 6th'' (Fr+6 or Fr<sup>4</sup><sub>3</sub>) has the same notes as the Italian 6th, plus the M2 note above the key's tonic (m6 U M2 a4). In C Major, that's (A{{f}} C D F{{s}}).
R M3 a4 a6
-M3- -M2- -M3
----tt----
----a4----
-------a6-------
All these notes are found in the [[Exotic Scales#Whole Tone|whole tone scale]], giving it a somewhat atonal kind of feel; however, it still retains its sub-dominant harmonic function within the context of a progression.
===== German =====
The ''German 6th'' (Gr+6 or Gr<sup>6</sup><sub>5</sub>) similarly takes the Italian and adds a note, but here the note is the m3 above the key's tonic note (m6 U m3 a4). In C Major, that's (A{{f}} C E{{f}} F{{s}}).
=== Neapolitan Chord ===