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The cadential 6/4: a tonic chord that isn't
Spell it and it looks like a tonic triad — I or i — with the fifth in the bass. Listen to it and it behaves like nothing of the sort: the cadential 6/4 always leans straight into the dominant, so theorists teach it as a decorated V rather than a real tonic. Scanning our corpus (54 pieces, including all 36 WTC preludes) for exactly that shape caught it 42 times across 23 pieces — every single instance resolving I64 → V or V7, never anywhere else.
Practice with the pieces that use it →
The census
How often each piece in the corpus reaches for the formula, ranked by how much it happens:
| piece | occurrences |
|---|---|
| Sonata in C, K. 545 | 5 |
| The Merry Peasant (Album for the Young, Op. 68 No. 10) | 5 |
| Prelude 5 in D major (BWV 850) | 4 |
| Prelude 3 in C-sharp major (BWV 848) | 3 |
| Prelude 7 in E-flat major (BWV 876) | 3 |
| Sonatina in G, Anh. 5 No. 1 | 2 |
| Air Napolitain "Santa Lucia" | 2 |
| Sonata No. 11, K. 331 — Alla Turca | 2 |
| Prelude 14 in F-sharp minor (BWV 883) | 2 |
| The Entertainer | 1 |
| The Little Hunter's Song (Album for the Young, Op. 68 No. 7) | 1 |
| Moonlight Sonata, 1st Movement | 1 |
| Prelude 6 in D minor (BWV 851) | 1 |
| Prelude 12 in F minor (BWV 857) | 1 |
| Prelude 13 in F-sharp major (BWV 858) | 1 |
| Prelude 16 in G minor (BWV 861) | 1 |
| Prelude 17 in A-flat major (BWV 862) | 1 |
| Prelude 19 in A major (BWV 864) | 1 |
| Prelude 21 in B-flat major (BWV 866) | 1 |
| Prelude 23 in B major (BWV 868) | 1 |
| Prelude 4 in C-sharp minor (BWV 873) | 1 |
| Prelude 13 in F-sharp major (BWV 882) | 1 |
| Prelude 15 in G major (BWV 884) | 1 |
Sonata in C, K. 545 leans on it hardest — 5 separate cadential 6/4s, once at the end of nearly every phrase. Bach's WTC preludes supply most of the rest: 15 of the 23 pieces that use it at all are WTC preludes, almost always right before the final cadence.
Hear it happen
Each link opens the piece in the harmony player, chords labeled — the bar numbers below point at the moment the "tonic" resolves into the dominant it was always aiming for.
- Sonata in C, K. 545 W. A. Mozart 5 cadential 6/4s
- The Merry Peasant (Album for the Young, Op. 68 No. 10) R. Schumann 5 cadential 6/4s
- Prelude 5 in D major (BWV 850) J. S. Bach 4 cadential 6/4s
- Prelude 3 in C-sharp major (BWV 848) J. S. Bach 3 cadential 6/4s
- Prelude 7 in E-flat major (BWV 876) J. S. Bach 3 cadential 6/4s
- Sonatina in G, Anh. 5 No. 1 L. v. Beethoven 2 cadential 6/4s
- Air Napolitain "Santa Lucia" C. Czerny 2 cadential 6/4s
- Sonata No. 11, K. 331 — Alla Turca W. A. Mozart 2 cadential 6/4s
- Prelude 14 in F-sharp minor (BWV 883) J. S. Bach 2 cadential 6/4s
- The Entertainer S. Joplin 1 cadential 6/4
- The Little Hunter's Song (Album for the Young, Op. 68 No. 7) R. Schumann 1 cadential 6/4
- Moonlight Sonata, 1st Movement L. v. Beethoven 1 cadential 6/4
- Prelude 6 in D minor (BWV 851) J. S. Bach 1 cadential 6/4
- Prelude 12 in F minor (BWV 857) J. S. Bach 1 cadential 6/4
- Prelude 13 in F-sharp major (BWV 858) J. S. Bach 1 cadential 6/4
- Prelude 16 in G minor (BWV 861) J. S. Bach 1 cadential 6/4
- Prelude 17 in A-flat major (BWV 862) J. S. Bach 1 cadential 6/4
- Prelude 19 in A major (BWV 864) J. S. Bach 1 cadential 6/4
- Prelude 21 in B-flat major (BWV 866) J. S. Bach 1 cadential 6/4
- Prelude 23 in B major (BWV 868) J. S. Bach 1 cadential 6/4
- Prelude 4 in C-sharp minor (BWV 873) J. S. Bach 1 cadential 6/4
- Prelude 13 in F-sharp major (BWV 882) J. S. Bach 1 cadential 6/4
- Prelude 15 in G major (BWV 884) J. S. Bach 1 cadential 6/4
Go deeper
- Train your ear to catch it → Our ear-training site drills hearing the second-inversion tonic resolve into the dominant until the "not really a tonic" feeling is unmistakable.
- The theory: the cadential 6/4 → Why it's classified as dominant function despite the tonic spelling — the full chapter on our theory site.
- How those cadences actually land → The census of every piece's final two chords — the cadential 6/4 above is usually the gesture that sets one up.
- Learn a piece that uses them → The practice ladder loops eight bars at a time — hear the harmony slowly, read along, then play at tempo.