111 Introduction to Augmented Sixth Chords

Definitions and Solfege

Augmented sixth chords are called this because they are bordered by the interval of an augmented sixth between le and fi.

There are three types of augmented sixth chord:

• Italian sixth (le-do-fi), commonly analyzed using the abbreviation It+6
• French sixth (le-do-re-fi), abbreviated Fr+6
• German sixth (le-do-me-fi), abbreviated Ger+6

This is what the chords look like side by side:

Theory: Harmonic Function

Augmented sixth chords typically precede the dominant. For voice-leading reasons such as  avoiding parallel perfect consonances, i 6/4 will often come between the augmented sixth and the dominant (though, as you know, the cadential 6/4 itself has dominant function.) This is particularly true when the chord in question is a German sixth chord.

Theory: Voice-Leading Procedure

When the augmented sixth precedes V, le typically resolves down to sol, and fi typically resolves upwards to sol. But when the augmented sixth chord precedes V⁷, fi can resolve downwards to fa.

In Context: Piano Practice

Play the following cadential progressions on the piano, taking careful notice of the solfege degrees and voice-leading. How do the chords resolve? Experiment: try to change one type of augmented sixth chord into another type by adding or subtracting re or me as appropriate. How does this affect the voice-leading?

Ear Training – Tips for Identification in Harmonic Dictation

• All augmented sixth chords: listen for le (resolving to sol on the next chord) in the bass voice.

• The Italian sixth only has 3 tones; therefore, color is much less “rich” than the other two types of augmented sixth chord. It is common to confuse the Italian and German sixth chords, so be sure to practice them both on the piano until you can differentiate their colors confidently.

• The French sixth sounds very dissonant because it’s composed of a partial whole-tone collection. Listen for the “impressionistic” tone color that we associate with the whole-tone scale. The French sixth is also a symmetrical chord, being composed of two major thirds separated by a major second.

• The German sixth chord is easily confused with the Italian sixth, but it is a much richer chord because it has 4 tones. Note: the German sixth chord has the same pitch classes as a major-minor chord in root position (Mm7), but of course it has a different function and different enharmonic spelling.

In Context – More Piano Practice

In this Italian sixth chord, do is doubled (since the Italian sixth chord only has 3 tones, and do, being the most “stable” tone, is the logical doubling choice). Experiment: what would happen if you changed the tenor voice to re or me to form a French or German sixth chord? Play around with the chords at the piano to see how you can use different types of augmented sixth chords to change the color of the harmony.

In the next example, the German sixth chord is followed by i 6/4 (to avoid parallel perfect fifths). This presentation is common for reasons of good voice-leading. Notice how le resolves to sol in the bass as usual, but fi (in the alto voice) resolves upwards to sol.

In Context – Singing

Prepare this material carefully, because you may be required to perform it in a sight singing exam. Experiment: can you perform the exercises successfully in a variety of different keys?

• In the first example, we build a German augmented sixth chord first by singing a partial descending scale that will take us to le. Now that we have the bass note of the chord, we build a major triad to form chord VI. Next, we add fi to create a complete German augmented sixth chord. Remember these pitches, because now we will subtract me to create an Italian augmented sixth chord. These can be hard to sing because of the tritone between do and fi, but if you’ve given yourself a pre-conceived structure from previously singing the German augmented sixth chord, it becomes much easier.

• In the second example, we will use a different procedure for navigating the tones of the French augmented sixth chord. Many learners find this chord harder to sing because of its dissonance. In this exercise, we will repeat the previous procedure for finding le from a given do. Then we will build a whole-tone scale from which we can select the tones of the French augmented sixth chord. Go slow, but not so slow that you forget all your previous pitches. The key to success is remembering where you’ve been while audiating where you’re about to go.