Augmented Sixth Chord Calculator and Explanation

An augmented sixth chord calculator identifies the notes in an Italian, French, or German augmented sixth chord from a chosen key and spelling convention. Enter the tonic pitch class and chord type; the calculator returns the chord’s notes, including the enharmonically equivalent raised fourth that typically resolves outward to the dominant.

Formula

This calculator needs more than a single numeric output to show a correctly spelled chord. The pitch-class input and chord-type selector specify the musical ingredients; the result is expressed as note names and scale-degree relationships, not as a meaningful one-number calculation. The pitch class uses C=0, C♯=1, D=2, D♯=3, E=4, F=5, F♯=6, G=7, G♯=8, A=9, A♯=10, and B=11. The selector distinguishes the three common chord types.

In a major key, the shared augmented-sixth framework is ♭6–1–♯4. These three scale degrees form an augmented sixth between the bass ♭6 and upper ♯4. The chord type determines whether it includes an additional note:

• Italian: ♭6–1–♯4.
• French: ♭6–1–2–♯4.
• German: ♭6–1–♭3–♯4.

The formulas describe scale degrees, so the exact letter names depend on the key. For example, in C major, ♭6 is A♭ and ♯4 is F♯. The chord’s A♭–F♯ interval is an augmented sixth, even though those notes sound like the same pitches as G♯ and F♯’s enharmonic spelling does not turn the interval into a different function.

Worked Example

With the block’s default tonic value, 0 means C. Its default chord type is Italian. In C major, the scale degrees are C, D, E, F, G, A, B; the Italian augmented-sixth chord uses ♭6, 1, and ♯4:

1. Start with C major: C–D–E–F–G–A–B.
2. Lower scale degree 6, A, by a semitone: A♭.
3. Keep scale degree 1: C.
4. Raise scale degree 4, F, by a semitone: F♯.

The resulting chord is A♭–C–F♯, or ♭6–1–♯4 in C. A♭ to F♯ spans an augmented sixth. The required result is a note spelling and chord structure; it cannot be represented by the single numeric output field in the calculator specification.

What an Augmented Sixth Chord Is

Augmented-sixth chords are chromatic predominant chords in tonal harmony: they commonly appear before the dominant, often directly before a cadential six-four chord or a dominant harmony. Their characteristic outer voices are a lowered sixth scale degree in the bass and a raised fourth scale degree above it. In common-practice voice leading, those notes generally move outward by semitone to the dominant’s fifth and root.

In C major, A♭ commonly moves down to G while F♯ moves up to G. The two lines converge on the dominant’s root, G, in contrary motion. The inner notes support the harmony and must be handled carefully according to the surrounding voices and style.

The chords also occur in minor keys. In C minor, the same outer notes, A♭ and F♯, can be understood relative to C; the inner notes and context determine the chord’s type and interpretation. Always state the key and spelling convention when using a calculator, because a list of pitch classes alone cannot show harmonic function.

How the Three Types Differ

• Italian sixth (It+6): Three distinct chord members: ♭6, 1, and ♯4. In C, A♭–C–F♯. It is commonly doubled in four-part writing because it has three chord tones but must fill four voices.
• French sixth (Fr+6): Adds scale degree 2: ♭6, 1, 2, and ♯4. In C, A♭–C–D–F♯. Its extra tone gives it a distinctive sound and can make its relation to a dominant-seventh sonority especially noticeable.
• German sixth (Ger+6): Adds ♭3: ♭6, 1, ♭3, and ♯4. In C, A♭–C–E♭–F♯. In standard tonal writing, moving directly to a dominant can create parallel fifths; composers often use a cadential six-four chord or another voice-leading solution.

Names and spellings can vary with theoretical context. The German sixth, for instance, may be enharmonically respelled to function as a dominant seventh in a different harmonic setting. That reinterpretation is not the same as saying the two spellings have identical function in every passage.

How to Choose Notes and Read the Result

First select the key, then identify its scale degrees before altering any notes. A calculator or chart that accepts only a tonic pitch class can give a starting point, but enharmonic keys may require different written spellings. C♯ major and D♭ major can sound alike in equal temperament while producing different note names and accidentals on the page.

• Use the Italian type for the three-note form.
• Choose French when the chord includes scale degree 2.
• Choose German when it includes lowered scale degree 3.
• Check the bass and upper voice: they should form an augmented sixth by spelling, not merely an enharmonic equivalent such as a minor seventh.
• Check the next chord and voice leading. The label alone does not tell you whether the progression is well written.

Pitch-class numbers ignore octave and register. They also do not encode whether a note should be written as A♭ or G♯. For composition, analysis, or notation, use a key-aware result and confirm the spelling against the score’s harmonic function.

Common Mistakes and Limits

The most frequent error is treating an augmented sixth chord as any chord containing an interval that sounds like a minor seventh. In equal temperament, A♭–F♯ sounds like G♯–F♯, but the latter is spelled as a minor seventh. Augmented-sixth analysis depends on the interval’s notation and the voices’ expected outward resolution.

Another error is confusing chord type with inversion. Italian, French, and German name the added chord members, not the bass position. An augmented-sixth chord may be inverted or voiced with doubled notes, but its characteristic augmented-sixth relationship and harmonic role still need to be clear.

A calculator can identify a theoretical set of notes, but it cannot decide the best voice leading without context. It may not account for a passage’s mode, local tonicization, unconventional spelling, or a deliberate enharmonic reinterpretation. Treat its output as a starting point, then inspect the musical passage.

Frequently Asked Questions

What notes are in an augmented sixth chord?
The shared outer notes are ♭6 and ♯4. An Italian chord adds 1, a French chord adds 1 and 2, and a German chord adds 1 and ♭3.

How do I find an augmented sixth chord in C major?
Use A♭ for ♭6 and F♯ for ♯4. Add C for the Italian form, D for French, or E♭ for German.

Why is it called an augmented sixth?
The interval between its characteristic bass ♭6 and upper ♯4 is spelled as six letter steps and measures an augmented sixth. The spelling reflects its harmonic role and outward resolution.

Does an augmented sixth chord always resolve to V?
It commonly functions as a predominant and moves to the dominant, but context and musical style can lead to other progressions or enharmonic interpretations.

Is a German sixth the same as a dominant seventh?
It can be enharmonically respelled to match a dominant-seventh set of sounding pitches in equal temperament, but the spelling and harmonic function are different unless the context supports that reinterpretation.

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in tonic | Tonic pitch class (C=0, C#=1, D=2, D#=3, E=4, F=5, F#=6, G=7, G#=8, A=9, A#=10, B=11) | - | 0 | 0
sel type | Chord type (Italian=1, French=2, German=3) | Italian=1, French=2, German=3
out root | Tonic pitch class | semitones | tonic | 0