IV. Diatonic Harmony, Tonicization, and Modulation
IV. Diatonic Harmony, Tonicization, and Modulation
6/4 Chords as Forms of Prolongation
John Peterson
Key Takeaways
This chapter introduces three additional [latex]^6_4[/latex] chords beyond cadential [latex]^6_4[/latex].
- Passing (pass.) [latex]^6_4[/latex] involves a passing tone in the bass that has been harmonized by a [latex]^6_4[/latex] chord. It typically prolongs tonic or predominant harmonies, and it always occurs between two chords of the same function.
- Neighbor (n.) [latex]^6_4[/latex] involves a static bass above which two of the upper voices perform upper neighbor motion. It typically prolongs tonic or dominant harmonies, and the chords on both sides of it are always in root position.
- Arpeggiating (arp.) [latex]^6_4[/latex] involves a bass that arpeggiates through the fifth of the chord while the upper voices sustain the chord in some way. It may prolong any harmony, and we don’t typically bother recognizing it in analysis.
The table in below summarizes the characteristics of each of the three types of [latex]^6_4[/latex] that we advocate labeling in analysis.
So far, we’ve seen that the tonic (T) area is most commonly prolonged using dominant-function chords, especially inverted [latex]\mathrm{V^7}[/latex]s. In this chapter, we look at some additional, less common ways to prolong not only tonic chords, but also dominant and predominant chords. Earlier, we saw how [latex]^6_4[/latex] chords are treated in special ways because they contain a dissonance with the bass (the fourth). We’ve already learned about [latex]\mathrm{cad.^6_4}[/latex]; here, we turn to the three other ways [latex]^6_4[/latex] chords can be used: passing [latex]^6_4[/latex], neighboring [latex]^6_4[/latex], and arpeggiating [latex]^6_4[/latex]. Note that in analysis, whenever you encounter a [latex]^6_4[/latex] chord, you should stop and identify which kind it is (cadential, passing, neighboring, or arpeggiating) because the kind of [latex]^6_4[/latex] determines the label. For [latex]^6_4[/latex] chords, the Roman numeral by itself isn’t a sufficient label—the type also needs to be included.
Passing [latex]^6_4[/latex]
The passing (pass.) [latex]^6_4[/latex] is a [latex]^6_4[/latex] chord built on a passing tone in the bass ( ). It’s most commonly found prolonging tonic or predominant harmonies. Importantly, the chords on both sides of the [latex]\mathrm{pass.^6_4}[/latex] are always the same function (e.g., [latex]\mathrm{IV^6-pass.^6_4-ii^6}[/latex]), not of different function (e.g., [latex]\mathrm{IV^6-pass.^6_4-I}[/latex]).
demonstrates the steps for writing [latex]\mathrm{pass.^6_4}[/latex] to expand tonic, and and show several ways [latex]\mathrm{pass.^6_4}[/latex] can prolong the predominant area. Note that each of these progressions can also work backward (e.g., [latex]\mathrm{I^6-pass.^6_4-I}[/latex] also works).
To write with pass[latex]^6_4[/latex]:
- Write the entire bass. You should have three notes in stepwise motion where the first and last not