← Real Sight Reader · Chromatic harmony series
The augmented sixths: all 7 of them
Most chromatic chords are common enough to survey. Augmented sixths are rare enough to count: reduce our whole corpus — 57 pieces, Bach preludes to Chopin nocturnes — to its harmony, and exactly 7 appear. That rarity is the lesson: this is a special-occasion chord, the widest pre-dominant stretch tonal music has, and composers spend it where it counts.
Every sighting
- Chopin — Nocturne in C♯ minor (Op. posth.) French sixth
Three French sixths in one nocturne — each time the same Fr7 leaning into the dominant, the signature ache of the piece’s middle section.
- Mozart — Alla Turca (K. 331) German sixth
A German sixth used the classical way: maximum pre-dominant crunch right before the cadence, twice, at the same joint in each half.
- Bach — Prelude 12 in F minor (WTC II) German sixth
Bach reaches the same sonority from voice leading alone — a Ger7 spelled by lines, a century before it had a nationality.
- Bach — Prelude 14 in F♯ minor (WTC II) French sixth
The corpus’s other French sixth, tucked into a sequence — easy to read past, impossible to unhear once you know it’s there.
Go deeper
- The theory: augmented sixth chords → Italian, French, German — how each is spelled, why they all resolve outward to the dominant, and how to write them.
- The enharmonic trap, by ear → A German sixth is note-for-note a dominant seventh — until it resolves. Drill the difference.
- Learn the nocturne that uses three → Section by section on the practice ladder.