Augmented Sixth Chords
Italian, French, and German — three chromatic chords that share one job: squeeze inward from a wide, tense interval into the dominant.
What makes a chord an "augmented 6th"?
All augmented 6th chords are built on the lowered 6th scale degree (b6) in the bass, with an upper voice a major 3rd above it. Between the bass and the highest voice of the chord sits an augmented 6th interval — enharmonically the same size as a minor 7th, but spelled to resolve differently: both outer notes move outward by half step into an octave. In C major, b6 is Ab, and the augmented 6th above it lands on F# (spelled that way instead of Gb specifically so it can resolve upward into G).
Italian, French, and German
The three national nicknames describe how many notes fill in the middle of the chord:
| Type | Notes (in C) | Built from |
|---|---|---|
| Italian (It+6) | Ab – C – F# | b6, 1, #4 |
| French (Fr+6) | Ab – C – D – F# | b6, 1, 2, #4 |
| German (Gr+6) | Ab – C – Eb – F# | b6, 1, b3, #4 |
The Italian +6 is the sparest — just three notes. The French +6 fills in the 2nd scale degree for a brighter, whole-tone-flavored color. The German +6 fills in the b3 instead, creating a full four-note chord that sounds noticeably richer and more stable than the other two.
The German's secret identity
Spell the German +6 as Ab–C–Eb–Gb instead of Ab–C–Eb–F#, and it becomes indistinguishable from an Ab dominant 7th chord — same four pitches, different spelling and function. That enharmonic overlap is exactly what lets composers pivot a German +6 into a completely unrelated dominant 7th chord and land in a distant key, a favorite trick called enharmonic modulation.
Common questions
What is an augmented 6th chord?
A chromatic pre-dominant chord built on the lowered 6th scale degree, with an augmented 6th interval above it that resolves outward by half steps, usually into the dominant.
What's the difference between Italian, French, and German augmented 6th chords?
All three share the b6 bass and augmented 6th interval. Italian +6 has three notes, French +6 adds the 2nd degree, and German +6 adds the b3 for a fuller four-note chord.
Why is the German augmented 6th special?
It's enharmonically identical to a dominant 7th chord on the same bass note, letting composers reinterpret it to pivot into distant keys — enharmonic modulation.
Where do augmented 6th chords resolve?
The augmented 6th interval's outer voices move outward by half step to an octave, typically arriving on V, which resolves normally to the tonic.
Hear chromatic pre-dominants in any key
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