In C minor, you encounter the chord Ab–C–Eb–F#. A student labels it 'Ab7' (an Ab dominant seventh chord). Why is this label wrong, even though the pitches look identical to an Ab dominant seventh?
AThe student is correct — Ab7 and the German augmented sixth are the same chord and function identically
BThe label is wrong because Ab is not a valid chord root in C minor
CThe label is wrong because the spelling reveals the function: F# resolves up to G (dominant), while Gb in Ab7 would resolve down to F. Same pitches, different functions and spellings
DThe label is wrong because dominant seventh chords cannot appear in minor keys
The German augmented sixth (Ab–C–Eb–F# in C minor) is enharmonically identical to Ab7 (Ab–C–Eb–Gb), but the spelling determines the function. F# is the raised fourth scale degree of C, which resolves upward by half step to G (scale degree 5 — the dominant). Ab resolves downward by half step to G. Both voices converge on the dominant — the chord's function is pre-dominant, resolving to V. If respelled as Ab7, the Gb would resolve down to F, targeting Db major. Same notes on the keyboard; completely different harmonic destinations. The spelling is not optional decoration — it declares the chord's intent.
Question 2 Multiple Choice
What distinguishes the French augmented sixth from the Italian augmented sixth?
AThe French sixth uses the raised fourth in the bass; the Italian sixth puts the flattened sixth in the bass
BThe French sixth adds scale degree 2 to the Italian sixth's three notes (b6, 1, #4)
CThe French sixth omits scale degree 1 that is present in the Italian sixth
DThe French sixth replaces the augmented sixth interval with a minor seventh interval
The Italian augmented sixth contains exactly three pitch classes: the flattened sixth (b6), scale degree 1 (tonic), and the raised fourth (#4) — the two notes that form the augmented sixth interval plus the tonic. The French augmented sixth adds scale degree 2 to this collection, giving it four distinct pitch classes and a slightly more dissonant, colorful sound. The German augmented sixth instead adds the flattened third (b3), which produces the chord that is enharmonically equivalent to a dominant seventh. All three share the defining b6–#4 augmented sixth interval in the outer voices.
Question 3 True / False
Augmented sixth chords are pre-dominant harmonies — they resolve to the dominant (V), not directly to the tonic (I).
TTrue
FFalse
Answer: True
This is the defining functional characteristic of the entire augmented sixth family. The augmented sixth interval between b6 (bass) and #4 (upper voice) resolves outward by contrary half-step motion: b6 moves down to scale degree 5, and #4 moves up to scale degree 5. Both voices arrive on the same pitch — the dominant scale degree — making the resolution to V both acoustically powerful and harmonically unambiguous. These chords intensify the approach to the dominant, functioning as a chromatic intensification of the pre-dominant function (like an elaborated IV or ii chord).
Question 4 True / False
The augmented sixth interval in these chords resolves by both voices moving inward — converging toward the middle — to land on the dominant.
TTrue
FFalse
Answer: False
The resolution is outward, not inward. The bass (b6) moves down by half step to scale degree 5; the upper voice (#4) moves up by half step to scale degree 5. They converge on the same note (the dominant) but from opposite directions — one coming from below, one from above. This outward expansion is acoustically distinctive and is what gives augmented sixth chords their sense of urgent release. Inward resolution would mean the two notes moved toward each other; instead they both expand to land on the same pitch from opposite sides.
Question 5 Short Answer
How do composers exploit the enharmonic equivalence between the German augmented sixth and a dominant seventh chord, and why does spelling still matter?
Think about your answer, then reveal below.
Model answer: Composers reinterpret a German augmented sixth as a dominant seventh (or vice versa) to pivot between distantly related keys. For example, the German augmented sixth in C (Ab–C–Eb–F#) can be respelled as Ab7 (Ab–C–Eb–Gb) and resolved as a dominant seventh to Db major — a key far from C. The listener hears the same sonority but the harmonic destination suddenly shifts. Spelling matters because it signals resolution: F# points up to G (dominant of C), while Gb points down to F (third of Db). The two spellings declare completely different harmonic intentions even though the notes sound identical on a keyboard.
This technique appears frequently in Schubert and Beethoven, where a chord suddenly seems to 'warp' to a new key. The enharmonic pivot works because equal temperament makes F# and Gb acoustically indistinguishable — the ambiguity is real and audible. But in tonal analysis, the spelling is never arbitrary: it is the composer's declaration of where the chord is going. A student who conflates the two spellings will misread the modulation and be confused about the key structure.