- Group of chromatic predominant chords including:
- Italian +6 (It+6)
- French +6 (Fr+6)
- German +6 (Ger+6)
- All contain the interval of an augmented sixth between and (le and fi)
- No chord root
- Resolves to a root-position dominant chord
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 and (le and fi). The chart below summarizes the names associated with each augmented sixth chord given its scale degrees in addition to and (le and fi).
|+6 Type||Scale Degrees||Solfege|
|French||and||do & re|
(or and )
|do & me
(or do & ri)
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 and (le and fi) 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 +6 interval and their resolution. Notice that both notes of the augmented sixth interval are tendency tones, both resolve to , and both are also only a minor 2nd away from . Augmented sixth chords happen in both major and minor keys but are more common in minor keys.
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 at a cadence point. They may intensify the push toward half and authentic cadences and the chord may have a seventh and/or include a cadential . The example below shows all three types in a simple cadential setting (authentic cadence versions). Note that you can expect that will be the bass for this chord, but raised can be in any other voice. Notice that the Ger+6 is typically followed by a cadential 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 cadential chord. These examples all include four voice parts, so the Fr+6 and Ger+6 don’t require doubling to have something for each of the four voices but because the It+6 only includes 3 unique pitches, the tonic is typically doubled because it is not a tendency tone.
Connection to the lament-bass progression
When they precede a half cadence, they resemble a phyrgian half cadence and/or the where the chord is substituted with a +6 chord by replacing with (fa with fi). 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.
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 to can support this progression and if chords occur above those scale degrees and the chord of also contains , 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.
Ger+6 in major keys ( vs. – me vs. ri)
Because the Ger+6 chord contains ( a note diatonic to minor scales) it is often respelled in major keys to avoid writing the same letter name twice in a row with different accidentals—a practice that composers avoid so that the contour of a musical line can be shown visually (i.e., does the line go up or down). To do this with a Ger+6 chord, composers often change to (me to ri). Ger+6 typically resolve to a cadential which already contains (mi), so using instead allows for a clearer indication of the ascending motion of the line. The example below shows this variant spelling of the Ger+6.
Less common versions (Ger°3 & CT+6)
In the 19th century, composers introduced a variant of the Ger+6 which used in the bass instead of . As result the +6 interval is now inverted, making it a °3 instead. The Ger°3 is very similar to because they only have one note different between them. Ger°3 has (le) but has regular (la) and they both resolve to root-position .
Ernesto Nazareth’s tango “Remando” uses a in m. 60 as part of the cadential progression. Notice the stepwise bass motion in that measure from to and to in the next measure 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 should be considered embellishing given that context. As is typical with the german version, the dominant is of the cadential variety.
Augmented Sixth Chords Assignment
- Includes spelling, figured bass realization, 4-part voice-leading with Roman numerals, and analysis of musical excerpt.
A lament-bass progression refers to a variety of harmonic progressions that harmonize a descending bassline from Do down to Sol. The simplest diatonic version uses the bass notes Do-Te-Le-Sol and is harmonized by the progression i v6 iv6 V. Chromatic alternatives are common, many of which use the notes between the simple diatonic version (Do-Ti-Te and Te-La-Le). Le is sometimes harmonized by augmented sixth chords, and Te is sometimes harmonized by V42/iv. More elaborate versions harmonize all available notes between Do and Sol: Do-Ti-Te-La-Le-Sol.