Augmented 6th Chords Made EASY
Today, let’s look at one of the most misunderstood chords in common practice music: The Augmented 6th chord.
Okay, so it’s actually three chords; or maybe like three flavors of the same chord. There’s an Italian, a German, and a French; which sounds like the start of a bad joke, but it’s not.
But, before we can understand the chord, we need to understand a little bit more about chord function. In common practice music (western classical), the goal is largely to start on the tonic, move away from the tonic for a while, make your way to dominant, and then return to the tonic. Everything that I’m about to say is meant to be understood within the context of western classical music.
One of the things that makes the motion from dominant to tonic so strong is the presence of the leading tone - the seventh scale degree of the scale is a half-step below the tonic. In classical music, we might say something like "the leading tone ‘needs’ to resolve to the tonic, or it leads us to the tonic.
So, if a half-step is the most effective way to lead to tonic - then a half step is the best way to lead to dominant as well. And that’s where we get the idea of secondary dominants. Let’s look at an example, we’ll use C major. If we’re going to have a secondary dominant, we first need a primary dominant, which in C major is G major. G leads us to C by V-I motion, but also because of the B natural resolving to C.
What if we were to get to G major the same way? Once again, we’re looking for the dominant chord, which in the key of G major is D major. D major has a V-I motion to G major, and an F# leading tone to G. This would make D major the V chord of the V chord in C major. It’s the dominant of the dominant, or the secondary dominant. We can have secondary dominants that lead us to other chords as well; like a V/vi, or a V/IV - but they still work the same way: V-I motion, and a leading tone.
Okay great, that’s a pretty strong pull to the V chord. But what could we do to make it even stronger? That’s where we get augmented 6th chords. Because the only thing stronger than leading to the dominant by half-step is leading to the dominant by half-step in both directions.
Like I said in the opening, there are three main types of Augmented 6th chords: French, Italian, and German. However, theorists don’t really know where they came from, and they don’t really have anything to do with the country that they are named after - so don’t get too hung up on that. The most important thing is their construction and function…and consequently, their resolution.
Their function is twofold: 1) be Pre-dominant (meaning that it leads to the dominant chord), and 2) be Pre-cadential (meaning that it leads to a cadence). Of course, composers are always looking for new and creative ways to subvert those guidelines, but we won’t worry about those for now.
The Italian Augmented Sixth Chord
The Italian is the most straightforward in terms of construction. I’ll use solfege, because I think it helps us understand scalar function, but also because of a mnemonic device. It’s made up of do (1), fi (#4), and le (b6)…or, Bambi steak (doe filet). It’s a terrible joke, but I promise you won’t forget it.
The sharp 4 and the flat 6 form the interval of an augmented 6th, and that’s where this chord gets its name.
More importantly, both of those notes are a half step away from the dominant. So, when resolving this, those two will resolve outward to form an octave on the dominant. And typically the tonic note is doubled in a four part spelling, which also resolves outward to complete the V chord.
Here’s an example from a Beethoven Piano Sonata:
The French Augmented Sixth Chord
The French is like the Italian, but it has an additional note: the second scale degree (or, do-re-fi-le).
The association with France may have to do with this spelling. There’s a scale called the whole tone scale, which perhaps you guessed, is made up entirely of whole tones. All of the notes in the French Augmented Sixth chord fit within this whole tone scale (with some enharmonic rearrangement).
Anyway, the construction of the chord is unique because it is made up of two overlapping tritones - that means there is even more tension that needs to be resolved.
That makes the resolution a little different than the Italian. Like always, the augmented 6th resolves outward to form an octave on the dominant. The tonic note goes down to the leading tone, and the second scale degree is already a member of the V chord, so it stays where it is.
The German Augmented Sixth Chord
Finally, we have the German variety. Much like the French, it has an additional note, except this time its flat 3. (do-me-fi-le). That flat 3 causes a problem when we go to resolve it.
Once again, our augmented 6 resolves to an octave, the tonic goes down to the leading tone, and the flat-3 would need to resolve down to the second scale degree, but that would give us parallel 5ths.
Composers have come up with various ways of getting around this. Mozart, for example, would usually just let the parallel 5ths happen, resolving it the most logical way.
Many other composers elected instead to resolve to a I 6/4 chord instead of a V. Many theorists, especially classical theorists, would argue that the I 6/4 chord still has dominant function. This means that the #4 and b6 would resolve outward like normal, but the other two notes are already a member of the i chord in minor key, so they stay the same.
One other thing you’ll notice is that the German Augmented 6th chord (enharmonically) is the same as a Dominant 7th chord. So, what is the difference?
The Augmented 6th chord is most concerned with resolving the augmented 6th interval out to the dominant, where the Dominant 7th chord is most concerned with resolving the tritone, which resolves inward to the tonic.
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