AP® Music Theory · Unit 5 · Topic 5.7
Passing, Pedal, and Arpeggiated Six-Four Chords
A six-four chord is only stable when it decorates a harmony rather than stands as its own root. Passing, pedal, and arpeggiated six-fours are three such decorative uses, each defined by what the bass is doing.
Second-inversion triads put the fifth of the chord in the bass, and that bass note wants to resolve rather than sit as a stable foundation. Because of that instability, six-four chords only show up in a handful of controlled situations, three of which are purely about decorating the bass line without implying a real change of root. In each case the six-four is not a destination, it is ornament.
A passing six-four fills in the gap between two chord tones a third apart in the bass. If the bass walks stepwise from C up to E, the note in between, D, needs harmonizing, and the six-four sonority built on D does that job while the harmony around it stays anchored to the same basic progression, often I - V6/4 - I6 or similar. A pedal six-four is different: the bass does not move at all. It holds one pitch while the upper voices step up to form a six-four sonority and then step back down to the original chord, so the bass acts like a pedal point under a built-in neighbor motion above it. An arpeggiated six-four happens when the bass itself leaps through the notes of a single held chord, say C up to E up to G, so the six-four is just one moment in an arpeggio, not a new harmonic event.
All three connect directly to the earlier point of this unit: six-four chords are never independent harmonies, they are ways of keeping the bass line interesting while the real harmonic motion happens elsewhere, usually still obeying the predominant-to-dominant-to-tonic logic the unit builds around.
Key terms
- Six-four chord
- A triad in second inversion, with its fifth in the bass.
- Passing six-four
- A six-four formed when the bass steps between two chord tones a third apart.
- Pedal six-four
- A six-four formed when the bass holds one pitch while upper voices move up and back.
- Arpeggiated six-four
- A six-four formed when the bass leaps through the notes of one held chord.
- Pedal point
- A sustained bass note held under changing harmony above it.
Watch it explained
- How it worksHow does a passing six-four harmonize the middle note of a three-note bass line?
- How it worksWalk me through a pedal six-four where the bass stays put and two voices step up and back.
- Worked exampleFind the type of six-four chord when the bass moves C, D, E under I, then V, then I6.
- Worked exampleFind the type of six-four when the bass arpeggiates C, E, G beneath a held tonic chord.
Check yourself
End of topic.