Volume I · Chapter 8B
Six-Four Chords
MUSIC 20A · C-ID MUS 120Chapter quiz →
In the musicianship bookChapter 8: Progressions, Phrases, and CadencesChapter 14: Six-Four Chords and Cadences
Introduction: The Unstable Inversion
In Chapter 4 we saw that a perfect fourth above the bass behaves like a dissonance. A triad in second inversion has exactly that: a fourth (and a sixth) above its bass. That's why six-four chords sound restless, and why composers use them in only a few specific, predictable ways.
Learn the four standard types below and you'll recognize nearly every six-four chord you meet. In each one, double the bass (the fifth of the chord), and expect the six-four to behave more like an embellishment of the chords around it than like a chord in its own right.
Click any example to hear it.
1. The Cadential Six-Four
The most important six-four chord appears at cadences. A tonic triad in second inversion (I64) sits over 5̂ in the bass, on a strong beat, and resolves to V over the same bass note. The upper voices slide down: the 6th above the bass falls to the 5th, and the 4th falls to the 3rd.
Although it looks like a tonic chord, it doesn't function as one: the bass is already on the dominant, and the whole gesture is really a V chord with two upper notes delayed. Many theorists label it V64–53 or Cad64 to show this; you may see either, alongside the plain I64–V.
- Approach it from a predominant (IV, ii, ii6) or from tonic.
- Put it on a stronger beat than its resolution to V.
- Keep the bass the same (or move it by an octave) as I64 becomes V.
- V may become V7 as the 8 (octave above the bass) moves down to 7.
2. The Passing Six-Four
A passing six-four harmonizes a bass line that moves by step between two positions of the same chord, most often I–V64–I6 (bass 1̂–2̂–3̂) or the reverse. It sits on a weak beat, and the upper voices usually move by step or hold.
3. The Pedal (Neighbor) Six-Four
In a pedal six-four the bass holds one note (often the tonic) while two upper voices move up by step and back: I–IV64–I. The 6/4 is an embellishment of the chord around it, and it's common in hymns and at the very end of pieces (the "amen" feel).
4. The Arpeggiated Six-Four
When the bass leaps among the notes of a single chord (as in a waltz accompaniment or an arpeggiated bass line), it will land on the fifth now and then. That momentary second-inversion sound is an arpeggiated six-four: it doesn't need special treatment, because the harmony hasn't changed.
Summary
| Type | Typical progression | Bass | Metric position |
|---|---|---|---|
| Cadential | PD → I64 → V → I | 5̂ held into V | Strong beat |
| Passing | I – V64 – I6 (or IV – I64 – IV6) | Steps through | Weak beat |
| Pedal (neighbor) | I – IV64 – I | Held | Usually weak |
| Arpeggiated | Any chord with a moving bass | Leaps within the chord | Any |
Whatever the type, double the bass, approach and leave the bass by step or by common tone (except in arpeggiation), and never use a six-four chord as a stable resting point.
Try It
This progression ends with a cadential six-four. Check it, then change the predominant to ii6 (bass F3, upper voices from D) and check again.