AP® Music Theory · Unit 5 · Topic 5.6
The Cadential Six-Four Chord
The cadential six-four stacks a sixth and a fourth above scale degree 5 in the bass, using tonic pitches that act as dissonances and step down into the fifth and root of V, delaying the dominant's arrival rather than sounding like tonic.
A cadential six-four looks like a tonic triad in second inversion: same three pitch classes, bass on scale degree 5 instead of 1. But spelling is not function. The bass sits under a sixth and a fourth, scale degree 1 and scale degree 3, and both of those upper notes are unstable. They are not sitting comfortably as chord members, they are leaning, waiting to fall. The sixth steps down to the fifth of V, and the fourth steps down to the third of V, while the bass stays put on scale degree 5 and becomes the root of the dominant. Nothing here acts like tonic. The whole chord exists to stall V's full arrival by one beat, building tension right before the cadence lands.
That stepwise descent is the mechanism worth tracking by ear and on paper: sixth to fifth, fourth to third, bass holding still. In a Roman numeral progression this is written V6-4 going to V, with the six-four resolving directly into the root-position dominant before tonic finally arrives. The bass is almost always doubled, since it is the one stable note in the chord, the anchor the dissonant upper voices resolve against.
This chord deepens the predominant-dominant-tonic story Unit 5 has been building. Predominant chords like ii or IV lead naturally into V. The cadential six-four inserts itself right at that dominant arrival, stretching out the moment of greatest tension so the eventual resolution to I feels stronger. It belongs to dominant function, not tonic, because its bass and its behavior both point toward V, even though its notes borrow tonic's face.
Key terms
- Cadential six-four
- A second-inversion tonic-spelled chord over scale degree 5 whose upper voices resolve down into the dominant triad.
- Predominant function
- The harmonic role of chords like ii and IV that lead into the dominant before the final tonic arrival.
- Six-four chord
- Any triad in second inversion, named for the intervals of a sixth and a fourth above its bass note.
- Resolution
- The stepwise motion of an unstable, dissonant note down or up into a stable chord tone.
- Doubling
- Writing the same pitch class in two voices at once, almost always the bass in a cadential six-four.
Watch it explained
- How it worksHow does a cadential six-four delay the dominant by placing a sixth and a fourth over scale degree 5?
- How it worksWalk me through the sixth and the fourth stepping down into the dominant triad.
- Worked exampleWalk me through writing a cadential six-four to V to I in D major with the bass doubled.
- Common mistakeWhy isn't the cadential six-four analyzed as a tonic chord in second inversion?
- Ties togetherHow does the cadential six-four's delay of the dominant deepen the predominant, dominant, tonic cycle of harmonic function?
Check yourself
End of topic.