Augmented 6Th Chords

The world of music theory is filled with complex structures, but few carry the dramatic weight and emotional impact of Augmented 6th chords. These harmonies, which emerged prominently during the Baroque and Classical periods, serve as a bridge between tension and resolution, pushing the listener toward a satisfying cadence. Understanding these chords is essential for any composer, arranger, or music theory student looking to add depth and sophistication to their work. Whether you are analyzing a Mozart sonata or writing your own orchestral piece, these chords provide an unmistakable sound that is deeply rooted in the history of Western art music.

Table of Contents

What Exactly Are Augmented 6th Chords?

At their core, Augmented 6th chords are chromatic chords that contain an interval of an augmented sixth. This interval is traditionally constructed by having a lowered sixth scale degree and a raised fourth scale degree. When these two notes sound together, they create a pungent, expectant sound that yearns to resolve outward to the octave. This outward motion—where the two notes move away from each other by a half-step—is the hallmark of the chord's function as a predominant harmony.

Typically, these chords resolve to a dominant chord (V). Because the notes are pulling toward the fifth degree of the scale, they create an incredibly strong magnetic pull that makes the following resolution feel inevitable and resolute. There are three primary types of augmented sixth chords, distinguished by their unique internal structure and the color they add to a composition.

The Three Primary Types

To master these harmonies, you must learn to distinguish between the Italian, French, and German variants. While they all share the fundamental interval of the augmented sixth, their internal notes vary, creating slightly different "flavors" of tension.

The Italian Sixth: This is the simplest version, consisting of only three notes: the lowered sixth scale degree, the tonic, and the raised fourth scale degree. It is lean, direct, and incredibly potent.
The French Sixth: This version adds a second scale degree to the mix, creating a more dissonant and "trippy" texture. It is often described as having a whole-tone quality.
The German Sixth: This chord includes the lowered third scale degree alongside the other notes. It sounds very similar to a dominant seventh chord but functions entirely differently due to its unique spelling and resolution.

💡 Note: The German Sixth chord is notorious for producing a "parallel fifths" error when resolving directly to a root-position V chord. To avoid this, composers often resolve it first to a cadential 6/4 chord.

Chord Type	Scale Degree Content	Primary Characteristic
Italian Sixth	b6, 1, #4	Stripped-back and intense
French Sixth	b6, 1, 2, #4	Dissonant and atmospheric
German Sixth	b6, 1, b3, #4	Harmonically rich and full

Voice Leading and Resolution Mechanics

The beauty of Augmented 6th chords lies in their strict voice-leading rules. Because the augmented sixth interval is highly dissonant, the ear expects it to resolve outward. In a standard resolution, the lowered sixth scale degree moves down to the fifth scale degree, while the raised fourth scale degree moves up to the fifth scale degree. This double-leading-tone motion creates a satisfying sense of arrival at the dominant.

Also read: Ideal Age For Adenoid Removal

When incorporating these into your music, keep these guidelines in mind:

Always ensure the augmented sixth interval is at the core of the vertical structure.
Allow the voices to move by half-step increments whenever possible for the smoothest resolution.
Use these chords to emphasize a specific cadential moment, such as the end of a phrase or a transition between sections.

💡 Note: While these chords are traditionally linked to minor keys, they are frequently borrowed for use in major keys by lowering the sixth scale degree chromatically.

Practical Applications in Modern Composition

While often associated with historical classical music, the logic behind Augmented 6th chords can be applied to modern genres, including film scoring and jazz fusion. Filmmakers often utilize the instability of the German sixth to suggest a moment of high stakes or uncertainty. In a cinematic context, these harmonies can represent a turning point in a narrative, forcing the audience to lean into the tension.

Tips for Ear Training

Recognizing these chords by ear takes practice, but the process becomes easier once you lock into the interval of the augmented sixth. When listening to pieces, try to identify the "crunch" of the augmented sixth interval resolving outward. If you hear a chord that sounds like a dominant seventh but feels like it is pulling somewhere else, you are likely hearing a German sixth. If the sound is thinner and more biting, look for the Italian or French variants.

Practice writing these chords in different keys on a piano or keyboard. By physically playing the notes and hearing the resolution, you will internalize the sound, making it a natural part of your harmonic vocabulary. Do not rush the process; focus on the spacing of the voices and how the interval expands to the dominant.

By mastering the use of these specialized harmonies, you gain a powerful tool that transcends stylistic boundaries. The ability to control tension and release is what separates basic songwriting from expert composition. These chords are not merely academic exercises; they are emotional catalysts designed to guide the listener through a narrative arc. Whether you are aiming for the dramatic flair of a Romantic-era symphony or the subtle tension of a modern score, integrating these structures allows you to manipulate harmonic gravity with precision. As you continue to experiment with different voicings and resolutions, you will find that the augmented sixth becomes an indispensable part of your creative toolkit, allowing you to craft moments of profound resolution that resonate long after the music stops.