Augmented sixth chords sit at a strange crossroads in music theory. They sound exotic yet familiar, pulling the ear forward with a tension that feels both ancient and theatrical. Composers from the Baroque era through the Romantic period reached for them when they wanted to heighten drama without sliding into full atonality.
Once you start hearing them in Mozart, Beethoven, or even film scores, you cannot unhear the itch they create right before a cadence.
The best way to understand them is to meet the main varieties in the order they tend to appear in real music. Each type carries its own flavor, its own set of voice-leading rules, and its own historical baggage. Learning these distinctions helps you spot them in scores, improvise them at the piano, and decide which one fits the emotional moment you are chasing.
The Main Varieties of Augmented Sixth Chords
1. Italian Sixth
The Italian sixth is the simplest and most common member of the family. It is built on the flattened sixth scale degree in a minor key, or the lowered sixth in major, and stacks a major third and an augmented sixth above it. In C minor that gives you A-flat, C, and F-sharp.
The chord has only three notes, which is why it feels so direct.
What makes it Italian is its economy. Composers loved how cleanly those outer notes, the flat sixth and raised fourth, want to resolve outward to the dominant. The A-flat drops to G while the F-sharp rises to G, creating an octave on the dominant root.
That bare octave resolution gives the Italian sixth its bright, almost operatic cry. You hear it everywhere in Verdi arias when the soprano is about to launch into a big cadence. The tradeoff is that three-note version can sound a little thin if you do not double the right note, usually the tonic, in four-part writing.
Still, its straightforwardness makes it the perfect gateway chord for anyone first exploring augmented sixths.
2. French Sixth
Next comes the French sixth, which adds a single note to the Italian recipe and suddenly the whole mood changes. Take the same A-flat and F-sharp from before, keep the C, and slip a D natural between them. Now you have A-flat, C, D, F-sharp.
The added second above the bass creates a pungent, almost jazzy clash that feels like it belongs in both Classical symphonies and later Impressionist works.
Debussy and Ravel were especially fond of the French sixth because that extra note lets the chord float instead of strictly resolve. You can let it drift into whole-tone scales or use it to color a dominant seventh with added tension. The French sixth also resolves beautifully to a dominant seventh instead of a plain triad, which opens up smoother chromatic lines.
Its one drawback is that the four distinct pitches make voice leading trickier in dense textures. You have to be careful not to create parallel fifths when the D moves to the dominant root. Get it right, though, and the chord delivers a sophisticated bite that the simpler Italian version cannot match.
3. German Sixth
The German sixth is the richest and most Romantic sounding of the standard three. It keeps the A-flat and F-sharp but replaces the middle note with E-flat, giving you A-flat, C, E-flat, F-sharp. That stack of thirds looks exactly like a dominant seventh chord built on the flat sixth scale degree.
In fact, it is enharmonically identical to an A-flat seventh chord.
This double identity is the German sixth’s secret weapon. Composers could pivot from a minor-key progression straight into the parallel major by treating the chord as V7 of the new key. Beethoven used this trick constantly to modulate without sounding abrupt.
The chord’s full, almost Brahmsian thickness also lets you double the bass or the third for extra power. The catch is that its resolution to the dominant can produce parallel fifths if you are not paying attention, a problem so famous that theory textbooks still call it the “German sixth problem.” Many writers solved it by first moving to a cadential six-four chord, which absorbs the parallel motion and keeps the resolution clean.
4. Neapolitan Sixth
Beyond the big three, the Neapolitan sixth sometimes gets lumped into the augmented-sixth conversation even though it is not technically one. It is a major triad built on the lowered second scale degree, usually in first inversion. In C minor that is D-flat, F, A-flat with F in the bass.
The reason it feels related is that the outer interval between bass and soprano is a diminished seventh, which shares the same restless quality.
What separates the Neapolitan is its pre-dominant function rather than its dominant pull. It almost always moves to a dominant or cadential six-four rather than resolving outward like a true augmented sixth. Still, you will find passages where composers chain a Neapolitan directly into an Italian or German sixth, creating a chromatic staircase that heightens anticipation.
Chopin loved this combination in his nocturnes. The Neapolitan adds a dark, almost funereal color that the other chords cannot supply on their own.
5. Doubly Augmented Sixth
Less common but worth knowing is the doubly augmented sixth, sometimes called the Swiss sixth in older texts. It raises the second note of the German sixth by a half step, turning the perfect fifth into an augmented fifth. In our C minor example the chord becomes A-flat, C-sharp, E-flat, F-sharp.
That extra raised note creates an even stronger leading-tone pull toward the dominant.
You mostly encounter these in late Romantic music when composers were stretching tonality as far as it would go. The doubly augmented version lets you delay resolution for several beats while the ear begs for the dominant chord. Its rarity is part of its power.
When it appears, the listener feels the harmonic ground shift underfoot. The tradeoff is that it is difficult to prepare smoothly without sounding arbitrary, so it works best in sequences or after a German sixth has already established the augmented-sixth sound.
6. Enharmonic German Sixth
Finally there is the enharmonic German sixth, a clever respelling that lets the chord resolve in an unexpected direction. Instead of treating F-sharp as an augmented sixth, you write it as G-flat and treat the whole sonority as a dominant seventh of the Neapolitan. This opens a back door into distant keys.
Brahms used this move in his chamber music to slip from one tonal center to another without breaking stride.
The technique demands fluent enharmonic thinking at the keyboard, but once you master it the augmented sixth stops being a fixed destination and becomes a crossroads. You realize the chord is less a single object than a flexible bundle of tendencies that can point in several directions at once.
These different augmented sixths are not museum pieces. They still surface in modern film scores whenever a composer needs to signal impending fate or sudden revelation. The next time you sit at the piano, try sliding from a minor iv chord into an Italian sixth and then into its German cousin.
Feel how each change alters the temperature of the room. That small experiment will teach you more than any textbook definition.
Mastering the flavors of the augmented sixth family gives you a set of colored lights you can shine on any progression. Used well, they turn ordinary cadences into moments that feel inevitable and surprising at the same time. That combination, inevitability wrapped in surprise, is exactly why these chords have held composers spellbound for three centuries and why they will keep working their magic for centuries more.