V. Chromaticism

Augmented Sixth Chords

Brian Jarvis

Key Takeaways

• Group of chromatic predominant chords including:
• Italian +6 $(\mathrm{It^{+6}})$
• French +6 $(\mathrm{Fr^{+6}})$
• German +6 $(\mathrm{Ger^{+6}})$
• All contain the interval of an augmented sixth between le–fi $(\downarrow\hat{6}–\uparrow\hat{4})$
• No chord root
• Resolves to a root-position dominant chord

Brief Overview:

Augmented sixth chords are a category of chromatic, predominant harmonies whose name is derived from the inclusion of a very specific interval, the augmented sixth between le–fi $(\downarrow\hat{6}–\uparrow\hat{4})$. The chart below summarizes the names associated with each augmented sixth chord given its scale degrees in addition to le–fi $(\downarrow\hat{6}–\uparrow\hat{4})$.

+6 Type Scale Degrees Solfege
Italian $\hat{1}$ do
French $\mathrm{\hat1\ and\ \hat2}$ do & re
German $\mathrm{\hat1\ and\ \downarrow\hat3\ (or\ \hat1\ and\ \uparrow\hat2)}$ do & me
(or do & ri)

Example 1. Overview of the different augmented sixth chords.

Context

While the individual names (Italian, French, and German) are more colorful than historical, the category title, augmented sixth, is quite fitting because the interval of the augmented sixth is contained within each type. Up until this point, you’ve probably grown accustomed and quite comfortable with determining a chord’s Roman numeral by finding its root. Well, augmented sixth chords are not typically categorized by root. Instead they are simply identified as chords that have the augmented sixth between le–fi $(\downarrow\hat{6}–\uparrow\hat{4})$ and they often have a few other notes that distinguish one type from the next (details below). This emphasizes the importance of this unique interval above all, making the additional notes more of a detail. The example below shows the specific scale degrees of the +6th interval and their resolution. Notice that both notes of the augmented sixth interval are tendency tones, both resolve to sol $(\hat{5})$, and both are also only a minor 2nd away from sol $(\hat{5})$. Augmented sixth chords happen in both major and minor keys but are more common in minor keys.

Example 2. Standard voice leading of the augmented-sixth interval.

Augmented sixth chords are another strategy for creating harmonic intensification with chromaticism. They are mostly used as a predominant harmony (though they can serve an embellishing function as well, see common-tone chords) and lead directly to root-position $\mathrm{V}$ at a cadence point. They may intensify the push toward half and authentic cadences and the $\mathrm{V}$ chord may have a seventh and/or include a $\mathrm{cad.^6_4}$. The example below shows all three types in a simple cadential setting (authentic cadence versions). Note that you can expect that le $(\downarrow\hat{6})$ will be the bass for this chord, but fi $(\uparrow\hat{4})$ can be in any other voice. Notice that the $\mathrm{Ger^{+6}}$ is typically followed by a $\mathrm{cad.^6_4}$which serves to offset the parallel perfect fifths that would have happened between G-D and F♯-C♯. However, the other types might also include a $\mathrm{cad.^6_4}$chord. These examples all include four voice parts, so the $\mathrm{Fr^{+6}}$ and $\mathrm{Ger^{+6}}$ don’t require doubling to have something for each of the four voices but because the $\mathrm{It^{+6}}$ only includes 3 unique pitches, the tonic is typically doubled because it is not a tendency tone.

Example 3. All three types of augmented sixth chords in a cadential context.

Connection to the lament-bass progression

When they precede a half cadence, they resemble a phyrgian half cadence and/or the where the $\mathrm{iv^6}$ chord is substituted with a +6 chord by replacing fa with fi $(\hat{4}$ with $\uparrow\hat{4})$. The example below shows a few versions of the lament bass and it illustrates how just one small change to the standard lament-bass progression can introduce an augmented sixth chord.

Example 4. Examples of replacing $\mathit{iv^6}$ with an augmented sixth chord in lament-bass progressions.

Recognizing +6 chords when analyzing

Because +6 chords are not root-based like you’re used to, you need another strategy to find them. If you try to stack the chord in thirds and determine the quality that way, you’ll run into a confusing issue because the chord will contain the interval of a diminished 3rd instead of just a combination of major and minor thirds like usual. The easiest method is simply to memorize that the bass motion le–sol $(\downarrow\hat{6}-\hat{5})$ can support this progression and if chords occur above those scale degrees and the chord of le $(\downarrow\hat{6})$ also contains fi $(\uparrow\hat{4})$, then you’ve likely identified an augmented sixth chord. From there, just determine the specific subtype (Italian, French, or German) by looking at the remaining chord members and that should take care of it.

$\mathrm{Ger^{+6}}$ in major keys: me vs. ri $(\downarrow\hat{3}$ vs. $\uparrow\hat{2})$

When a $\mathrm{Ger^{+6}}$ is used in major keys, me $(\downarrow\hat{3})$ is often respelled to avoid writing the same letter name twice in a row with different accidentals, since $\mathrm{Ger^{+6}}$ typically resolves to a $\mathrm{cad.^6_4}$, which already contains mi $(\hat{3})$. Using ri $(\uparrow\hat{2})$ instead of me $(\downarrow\hat{3})$ also allows for a clearer indication of the ascending motion of the line. The example below shows this variant spelling of the $\mathrm{Ger^{+6}}$.

Example 5. Alternative spelling of the $\textit{Ger^{+6}}$] chord in major keys.

Less common versions ($\mathrm{Ger^{o3}}$ & $\mathrm{ct^{+6}}$)

In the 19th century, composers introduced a variant of the $\mathrm{Ger^{+6}}$ which used fi $(\uparrow\hat{4})$ in the bass instead of le $(\downarrow\hat{6})$. As a result, the +6 interval is now inverted, making it a °3 instead. The $\mathrm{Ger^{o3}}$ is very similar to $\mathrm{vii^{o7}/V}$ because they only have one note different between them. $\mathrm{Ger^{o3}}$ has le $(\downarrow\hat{6})$ but $\mathrm{vii^{o7}/V}$ has la $(\natural\hat{6})$ and they both resolve to root-position $\mathrm{V}$.

Example 6. Using the $\mathit{Ger^{o3}}$.

Musical Example

Ernesto Nazareth's tango "Remando" uses a $\mathrm{Ger}^{+6}$ in m. 60 as part of the cadential progression. Notice the stepwise bass motion beginning in that measure la–le–sol $(\hat6-\downarrow\hat6-\hat5)$ as a technique to approach the augmented sixth chord by step in the bass. The melody of this dance features many accented passing tones so the C♯ during the $\mathrm{Ger^{+6}}$ should be considered embellishing given that context. As is typical with the $\mathrm{Ger^{+6}}$, the dominant is of the $\mathrm{cad.^6_4}$variety.

Example 7. Ernesto Nazareth, Remando (excerpt starts at 1:48). German augmented sixth chord as part of a cadential progression.

Assignments
1. Augmented Sixth Chords (.pdf, .docx.) Asks students to spell augmented sixth chords, realize figured bass, write 4-part voice-leading with Roman numerals, and analyze a musical excerpt. Audio 1 - Frederic Chopin, Audio 2 - Scott Joplin (excerpt starts at 0:56).