Questions: Augmented Sixth Chord Recognition by Ear

Question 1

While listening to a Romantic-era piano piece, you hear a chord resolve to V with both outer voices moving by half step in contrary motion, arriving on the same pitch class an octave apart. What type of chord most likely preceded the V?

• A. A diminished seventh chord — it also has strong voice-leading pull toward V
• B. A Neapolitan sixth — its bass resolves down by half step to V
• C. An augmented sixth chord — the defining feature is its outward half-step resolution to an octave on V
• D. A secondary dominant — the tritone in V7/V resolves similarly

Answer: (C)

The defining gestural fingerprint of augmented sixth chords is exactly this contrary-motion half-step expansion to an octave on V. The augmented sixth interval (one semitone wider than a major sixth) contracts outward: the lower pitch rises a half step and the upper pitch falls a half step (or vice versa), and both land on the same pitch class an octave apart. While diminished sevenths and secondary dominants have their own strong voice-leading, they do not produce this specific contrary-motion half-step-to-octave resolution.

Question 2

The German augmented sixth chord is frequently mistaken for a dominant seventh chord by ear. What is the structural reason for this confusion?

• A. Both chords resolve to I, so their function is identical in most contexts
• B. The German sixth contains the same four pitch classes as some dominant seventh chord, just spelled enharmonically
• C. The German sixth is built on the same scale degree as the dominant (scale degree 5)
• D. Both chords consist entirely of minor thirds stacked above the bass

Answer: (B)

The German augmented sixth (e.g., Ab–C–Eb–F# in C major) is enharmonically equivalent to a dominant seventh chord (Ab–C–Eb–Gb = Ab7). The pitches sound identical; only their spelling and resolution differ. This is why the German sixth can function as a harmonic surprise — when you hear what sounds like a V7 but it resolves in an unexpected direction, you may be hearing a German sixth. The enharmonic equivalence is precisely what makes it so effective as a chromatic pivot.

Question 3

Augmented sixth chords are characterized by their outer voices moving outward by half step in contrary motion to arrive on an octave when resolving to V.

• T. True
• F. False

Answer: True

True. This outward contrary-motion resolution is the defining gestural and aural feature of the augmented sixth chord family. The augmented sixth interval expands to an octave: one voice rises by half step and the other falls by half step, both landing on the same pitch class (typically scale degree 5 when resolving to V). Learning to hear this specific gesture — the taut outward expansion — is the key to recognizing augmented sixths by ear before conscious analysis.

Question 4

The French augmented sixth sounds nearly identical to a dominant seventh chord by ear, which is why it is the type most easily confused with V7.

• T. True
• F. False

Answer: False

False. It is the *German* augmented sixth that is enharmonically equivalent to a dominant seventh chord — they contain exactly the same four pitch classes, just spelled differently. The French sixth (scale degrees b6–1–2–#4) has a more dissonant, ambiguous sound due to the added scale degree 2, but it does not resemble V7. The Italian sixth, with only three distinct pitch classes, is the most exposed and simple-sounding of the three.

Question 5

Why is the augmented sixth interval — rather than any other distinctive interval — the defining sound of this chord family, and what happens to it on resolution?

Model answer: The augmented sixth interval (enharmonically a minor seventh) spans one half step wider than a major sixth, creating an intense outward tension. On resolution to V, the lower note (b6) rises by half step to scale degree 5 and the upper note (#4) also rises by half step to scale degree 5 — both voices converge on the same pitch class an octave apart in contrary motion. This double half-step pull in opposite directions gives the chord its characteristic 'straining' quality: two voices stretched taut that snap to rest when the interval expands to an octave.

The key point is that the augmented sixth interval has half-step resolution tendency in *both* directions simultaneously — the lower pitch must resolve up and the upper pitch must resolve up (because #4 leads to 5). This contrary-motion double half-step expansion is unique among common chord types and is what gives augmented sixth chords their expressive intensity and directional clarity in Romantic harmony.