Augmented 6th chords have long stood as a powerful and expressive tool in tonal music. They create immediate tension before the arrival of the dominant harmony, pulling the ear forward with colour, warmth, and a sense of anticipation. In this guide we explore the anatomy, history, and practical application of the augmented 6th chords family—including Italian, French, and German varieties—and show how to write and voice them effectively across keys and genres. Whether you are a student, composer, or arranger, understanding these chords will deepen your harmonic palette and sharpen your ability to shape musical progression.
What are the Augmented 6th Chords?
In tonal harmony, augmented 6th chords are a class of predominant chords whose defining feature is an interval spanning an augmented sixth between two notes. This interval traditionally resolves outward to the dominant harmony, creating a strong pull toward the dominant chord and, consequently, a compelling sense of motion in the music. The augmented 6th chord is not a single fixed triad; there are several well-known variants, each with its own characteristic set of notes and realisation in different keys.
There are three principal types commonly discussed in theory and practice: Italian augmented 6th chords, French augmented 6th chords, and German augmented 6th chords. Each type can be explained in terms of its scale-degree content, which makes it easier to recognise and spell in any given key. In the discussion below, we will use C major as a reference key to illustrate the intervals and move toward standard voice-leading patterns.
Italian Augmented 6th Chords (It+6)
The Italian augmented 6th chords are the simplest standard form of the family. They are built from three notes: the lowered sixth scale degree, the tonic, and the raised fourth scale degree. In C major, this yields the notes Ab – C – F#. This triad emphasises the two crucial notes around the augmented sixth: the interval between Ab and F# forms the distinctive augmented sixth that resolves to the dominant.
- In C major: It+6 = Ab – C – F#
- Voice-leading idea: Ab typically moves down to G (the dominant’s root), F# moves up or down to G (the dominant’s root or tense leading tone), and C can move to B to reinforce the G major triad.
Classic It+6 usage is to resolve to the dominant region, often preparing a V or V7 harmony. The resolution is a defining feature: the chromatic upper movement into the dominant creates forward momentum and a sense of arrival that is characteristic of classical tonal music.
French Augmented 6th Chords (Fr+6)
French augmented 6th chords add an additional colour tone to the Italian type. AFr+6 contains the lowered sixth, the tonic, the raised fourth, and the second scale degree. In C major this appears as Ab – C – D – F#. The presence of the note D (the supertonic) gives the French variant a broader sonority and more internal motion before resolution.
- In C major: Fr+6 = Ab – C – D – F#
- Voice-leading idea: Ab goes to G, F# goes to G, D may move to E or remain to become part of the ensuing dominant harmony, while C moves to B to support the G major triad or G7.
The Fr+6 often behaves like a stronger predominant than the It+6, thanks to the extra note (the 2). It provides a richer stepwise path into the dominant region and can be used to produce particularly convincing modulations and colour shifts.
German Augmented 6th Chords (Ger+6)
The German augmented 6th chords are the most expansive of the three main varieties. They contain the lowered sixth, the tonic, the lowered third, and the raised fourth. In C major the four notes are Ab – C – Eb – F#. This combination creates a dense sonority with a strong tendency to resolve to V or V7.
- In C major: Ger+6 = Ab – C – Eb – F#
- Voice-leading idea: Ab descends to G, Eb descends or steps to D, F# moves to F or G to align with the dominant, and C moves to B to reinforce the G chord tones.
The German variant’s extra third (Eb) contributes rich inner-voice motion and a slightly darker character compared with the Italian and French types. All three augmented 6th chord types share the same functional role: they preface the dominant harmony and heighten the sense of tension before resolution.
Voice Leading and Resolution: How Augmented 6th Chords Function
Understanding voice leading is essential for effectively employing augmented 6th chords. The hallmark of any augmented 6th chord is the outward resolution of the augmented sixth interval between the ♭6 and ♯4 degrees to the dominant harmony. In practice, this involves careful movement of voices so that the semitone steps create a smooth path into the dominant chord, often a G major harmony in the key of C major, or its equivalents in other keys.
Here are some practical guidelines to keep in mind when writing augmented 6th chords:
- Preserve common tones as much as possible to maintain a coherent texture. In It+6 (Ab – C – F#) in C major, the C commonly moves to B, while Ab and F# move to G to create a G-based harmony.
- Move the ♭6 downward by a semitone to become the dominant root (or lead into the root of the dominant chord). This is the primary outward motion that drives the resolution.
- Move the ♯4 by a semitone toward the tonic or through the leading tone into the dominant. In C major, F# may resolve to F or G, depending on the desired dominant texture.
- Consider resolving to V7 for the strongest pull. The fourth voice often participates by stepping to the third or fifth of the dominant for a stable preparation.
- Be mindful of voice crossing and spacing in close-voiced textures. In dense choral or string textures, distribute the voices to avoid clashes while still delivering the necessary chromatic movement.
Example in C major illustrating the It+6 resolving to V7 (G7):
It+6 (Ab – C – F#) moves to G7 (G – B – D – F). Ab descends to G, C descends to B, F# descends to F. The D can be supplied by an inner voice stepping into the dominant harmony, completing the dominant seventh chord.
Augmented 6th Chords in Minor Keys
In minor keys, augmented 6th chords still function as predominant units resolving to the dominant. The lowered sixth and raised fourth degrees are defined relative to the minor scale, and the resulting chords adapt their spellings accordingly. For example, in A minor, the It+6 would be F – A – D# (or Eb) depending on the exact spelling, with the same outward resolution toward E (the dominant in A minor). The choice between major and minor third in the It+6 family can colour the sonority, but the core functional relationship remains the same: a chromatic pre-dominant deliberately designed to unfold into the dominant harmony.
In practice, composers use augmented 6th chords in minor keys to evoke classical pathos, but they also appear in Romantic repertoire and even in modern pop arrangements where strong tonic–dominant relationships are desired, with the colour of the augmented sixth providing a distinct expressive palette.
Practical Writing Tips for Augmented 6th Chords
To make the most of the augmented 6th chords, keep these practical tips in mind when you are composing or arranging:
- Choose the variant based on desired colour. If you want a light predominant, It+6 may suffice; for richer sonority, Fr+6 or Ger+6 can be preferable.
- Plan the resolution to the dominant well in advance. The augmented sixth interval is the clue that the harmony will want to move toward V, so align your bass and inner voices accordingly to guarantee smooth motion.
- Be mindful of the practicalities of your instrument or ensemble. In piano literature, you can voice these chords with close intervals for intensity, or spread voices for clarity in orchestral or choral settings.
- Use these chords as a bridge for modulation. The strong pull to the dominant makes a seamless doorway to key changes, especially into keys a perfect fifth away or into closely related keys.
- Balance chromatic voice-leading with diatonic function. While the augmented 6th interval is chromatic, ensure the overall progression remains coherent within the tonal centre.
Augmented 6th Chords in Classical and Romantic Repertoire
In the Classical era, composers used augmented 6th chords to heighten tension before dominant progressions, resulting in memorable cadences and dramatic passages. In the Romantic period, the expressive potential of these chords expanded, with composers using extended chromatic vocabularies to push the boundaries of traditional harmony. In both eras, augmented 6th chords served as a versatile tool for shading, intensifying, and guiding harmonic motion. In modern concert music and film scores, their distinct colour remains a popular resource for creating moments of anticipation and release.
Augmented 6th Chords in Jazz and Popular Music
While the term is most closely associated with tonal classical harmony, the concept of a chromatic pre-dominant resolving to the dominant also appears, in spirit, in jazz and popular music. Jazz composers may substitute altered dominant colours or harmonise lines that imply an augmented 6th feel, using chromatic approach chords and borrowed scales to achieve a similar dreamlike tension before resolution. In popular music, you may hear moments that echo the functional pull of augmented 6th chords, especially as chord progressions move toward a strong V or V7 and then resolve into a final cadence. The colour and emotional charge of augmented 6th harmony can be utilised in song sections that require heightened drama or a sense of inevitability before the chorus or bridge releases.
Interpreting and Analysing Augmented 6th Chords
What should you listen for when analysing a passage featuring augmented 6th chords? Look for these cues:
- A deliberate chromatic movement between ♭6 and ♯4, forming the characteristic augmented sixth interval.
- A dominant-preparation function, with a clear aim toward the dominant harmony, often realised as V or V7.
- Voice-leading that moves by semitone steps toward the dominant, sometimes creating elegant melodic lines in the upper voices.
- Colour choice among It+6, Fr+6, and Ger+6 that informs mood. It+6 tends to be brighter; Fr+6 adds colour with the 2; Ger+6 gives a richer, darker texture.
By practising progressions that move from augmented 6th chords to V7 in multiple keys, you can develop fluency in recognising and employing these chords in a wide range of repertoires.
Examples: Concrete Progressions in C Major
Here are practical examples to illustrate how the It+6, Fr+6, and Ger+6 resolve to the dominant, using C major as the reference key. Remember that in real music you may encounter inversions, suspensions, and voice-leading adjustments, but the essential relationships hold.
Italian augmented 6th (It+6) to V7:
It+6: Ab – C – F# → V7: G – B – D – F
Voice-leading sketch (simplified): Ab → G, C → B, F# → F. The bass may move Ab to G (down a semitone) to support the dominant root, yielding a clean V7 sonority with G–B–D–F.
French augmented 6th (Fr+6) to V7:
Fr+6: Ab – C – D – F# → V7: G – B – D – F
Voice-leading sketch (simplified): Ab → G, D → D (common tone in some voicings), F# → F, C → B. The result is a strong dominant seventh everyone recognises as a strong resolution.
German augmented 6th (Ger+6) to V7:
Ger+6: Ab – C – Eb – F# → V7: G – B – D – F
Voice-leading sketch (simplified): Ab → G, Eb → D, F# → F, C → B. Again, the overall motion points decisively toward the dominant harmony.
Further Theoretical Notes and Nomenclature
In some theoretical treatments you may encounter augmented 6th chords described in terms of their enharmonic equivalents or in relation to the dominant seventh. The common thread is that these chords are chromatic, purposeful pre-dominants designed to resolve to the dominant. It is useful to remember that the names It+6, Fr+6, and Ger+6 identify the quality of the chord and its characteristic scale-degree content, but their realisation can be adapted to voice-leading needs and practical constraints in a given composition or arrangement.
Enharmonic reinterpretation is a notable feature of these chords: in many contexts the It+6, Fr+6, or Ger+6 may be heard as a dominant seventh with a particular spelling that highlights a leading-tone relationship. This reinterpretation is often used in advanced harmony to manage key changes or to integrate chromaticism with diatonic progressions in a coherent fashion.
Practical Exercises: Develop Your Command of Augmented 6th Chords
To build fluency with augmented 6th chords, try the following exercises:
- Write It+6, Fr+6, and Ger+6 in a series of keys, starting from tonic major and minor keys. Practice voice-leading to V7 in each case, ensuring smooth semitone steps toward the dominant.
- Experiment with close-voiced and spread-voiced textures. Observe how the sonority changes with different spacing and which voicings make the chromatic movement most transparent.
- Use the augmented 6th as a bridge to a modulation. Choose a target key a fifth away and map the It+/Fr+/Ger+6 to settle into the dominant of the new key.
- Analyse a piece from the Classical or Romantic repertoire to identify an It+6, Fr+6, or Ger+6 passage. Note the notes used, the resolution to the dominant, and how the voice-leading supports melodic lines.
Conclusion: Why Augmented 6th Chords Matter
Augmented 6th chords remain a cornerstone of tonal harmony because they deliver a distinctive and expressive way to propel music toward the dominant. Through the Italian, French, and German varieties, composers have access to a spectrum of colours that illuminate harmonic progressions, modulations, and cadences. The unique interval of the augmented sixth between ♭6 and ♯4 serves not only as a theoretical curiosity but as a practical engine for forward motion, tension, and emotional impact. By mastering their construction, voice-leading, and resolution, you will be equipped to enrich your own musical language with one of the most compelling tools in the harmonic repertoire.
Whether you are revisiting classical theory, arranging a modern piece, or composing a cinematic score, the augmented 6th chords offer a versatile and stylish means to shape musical tension and release. Practice, listen critically, and let the distinct colour of It+6, Fr+6, and Ger+6 guide your progress toward more sophisticated and satisfying harmonic textures.