Chapter Playlist

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 and fi [latex](\downarrow\hat6–\uparrow\hat4)[/latex]. Each augmented sixth chord (Italian, French, and German) contains one or two other scale degrees in addition to this interval, as summarized in the chart below and illustrated in Example 1. Augmented sixth chords can occur in both major and minor keys, but they’re more common in minor.

Example 1. Overview of the different augmented sixth chords.

Context

You’re now familiar with the process of finding a chord’s root for Roman numeral analysis, but augmented sixth chords are not typically categorized by root. Instead, they are identified as chords containing the augmented sixth between le and fi [latex](\downarrow\hat6–\uparrow\hat4)[/latex] and further categorized according to the other notes in the chord, as shown above. The names “Italian,” “French,” and “German” are more colorful than historical, but each chord is based on this characteristic interval.

Example 2 shows the specific scale degrees of the augmented sixth interval and their resolution. Notice that both notes in this interval are active notes: each one resolves to sol [latex](\hat5)[/latex] from a minor second away.

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 they lead directly to root-position V at a cadence point. They may intensify the push toward half and authentic cadences, and the V chord may have a seventh and/or include a [latex]\mathrm{cad.^6_4}[/latex]. Example 3 shows all three types in a simple cadential setting (authentic cadence versions). Note that you can expect that le [latex](\downarrow\hat6)[/latex] will be the bass for this chord, but fi [latex](\uparrow\hat4)[/latex] can be in any other voice. The Ger⁺⁶ is typically followed by a [latex]\mathrm{cad.^6_4}[/latex], which serves to offset the parallel perfect fifths that would have happened between G–D and F♯–C♯; the [latex]\mathrm{cad.^6_4}[/latex] may follow the other types as well. In a four-voice texture, the Fr⁺⁶ and Ger⁺⁶ don’t require doubling; in the It⁺⁶, which has only three unique pitches, the tonic is typically doubled because it is not an active note.

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

Connection to the lament-bass progression

When augmented sixth chords precede a half cadence, they resemble a phrygian half cadence and/or the lament-bass progression, where the iv⁶ chord is substituted with an augmented sixth chord by replacing fa with fi [latex](\hat4[/latex] with [latex]\uparrow\hat4)[/latex]. The example below shows a few versions of the lament bass, illustrating how just one small change to the standard lament-bass progression can introduce an augmented sixth chord.

Example 4. Examples of replacing iv⁶ with an augmented sixth chord in lament-bass progressions.

Recognizing augmented sixth chords when analyzing

Because augmented sixth chords are not root-based like you’re used to, you need another strategy to find them. Trying to determine the quality by stacking the chord in thirds would become confusing because it would contain a diminished third. The easiest method is simply to memorize that the bass motion le–sol [latex](\downarrow\hat6-\hat5)[/latex] can support this progression and if chords occur above those scale degrees and the chord with le [latex](\downarrow\hat6)[/latex] also contains fi [latex](\uparrow\hat4)[/latex], 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.

Ger⁺⁶ in major keys: me vs. ri [latex](\downarrow\hat3[/latex] vs. [latex]\uparrow\hat2)[/latex]

When a Ger⁺⁶ is used in major keys, me [latex](\downarrow\hat3)[/latex] is often respelled to avoid writing the same letter name twice in a row with different accidentals, since Ger⁺⁶ typically resolves to a [latex]\mathrm{cad.^6_4}[/latex], which already contains mi [latex](\hat3)[/latex]. Using ri [latex](\uparrow\hat2)[/latex] instead of me [latex](\downarrow\hat3)[/latex] also allows for a clearer indication of the ascending motion of the line. Example 5 shows this variant spelling of the Ger⁺⁶.

Example 5. Alternative spelling of the Ger⁺⁶ chord in major keys.

The German Diminished Third Chord

In the 19^th century, composers introduced a variant of the Ger⁺⁶ that used fi [latex](\uparrow\hat4)[/latex] in the bass instead of le [latex](\downarrow\hat6)[/latex] (Example 6). This inverts the augmented sixth interval, making it a diminished third instead. The Ger^o3 is very similar to vii^o7/V—the only difference is that Ger^o3 has le [latex](\downarrow\hat6)[/latex]  but vii^o7/V has la [latex](\hat6)[/latex]—and they both resolve to root-position V.

Example 6. Using the [latex]\mathit{Ger^{o3}}[/latex].

Musical Example

Ernesto Nazareth’s tango “Remando” (Example 7) uses a Ger⁺⁶ in m. 60 as part of the cadential progression. Notice the stepwise bass motion beginning in that measure, la–le–sol [latex](\hat6-\downarrow\hat6-\hat5)[/latex], 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 Ger⁺⁶ should be considered embellishing given that context. As is typical with the Ger⁺⁶, the following dominant chord is embellished with a [latex]\mathrm{cad.^6_4}[/latex].

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

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).