IV. Diatonic Harmony, Tonicization, and Modulation
IV. Diatonic Harmony, Tonicization, and Modulation
51
John Peterson
Key Takeaways
- Instead of using an inverted [latex]\mathrm{V^7}[/latex] chord to prolong tonic, composers sometimes use [latex]\mathrm{vii^{o7}}[/latex] or its inversions.
- Each inversion of [latex]\mathrm{vii^{o7}}[/latex] can be used in the same way as a particular inversion of [latex]\mathrm{V^7}[/latex]. The pairings of [latex]\mathrm{V^7}[/latex] and [latex]\mathrm{vii^{o7}}[/latex] are based on the bass note each chord harmonizes.
- [latex]\mathrm{vii^{o7}}[/latex] can be used anywhere that [latex]\mathrm{V^6_5}[/latex] or [latex]\mathrm{V^6}[/latex] can be used.
- [latex]\mathrm{vii^{o}\begin{smallmatrix}6\\5\end{smallmatrix}}[/latex] or [latex]\mathrm{vii^{o6}}[/latex] can be used in place of [latex]\mathrm{V^4_3}[/latex].
- [latex]\mathrm{vii^{o}\begin{smallmatrix}4\\3\end{smallmatrix}}[/latex] can be used in place of [latex]\mathrm{V^4_2}[/latex].
Overview
Earlier, we saw how the tonic can be prolonged using essentially four kinds of progressions, which we categorized according to their basslines (see the summary section of that chapter for a reminder). In this chapter, we consider an alternative way to harmonize those same tonic-prolongation bass lines using a harmony that can substitute for V7: the leading-tone chord. shows a passage from Mozart’s “Agnus Dei” that uses viio7 and its inversions to prolong tonic. Below the actual version, a recomposition shows that the bass line from the actual version can also be harmonized with V7 and its inversions. As you listen, notice the differences in color between the two versions. You may hear that the actual version is full of a wonderful tension that is less present in the recomposed version.
https://musescore.com/user/32728834/scores/6245135/embed
Before we address how this substitution works, here are three points we need to emphasize:
- The leading-tone chord as a triad is always used in first inversion viio6. This is because any other inversion creates a dissonance with the bass that composers tend to avoid.
- In minor, we need to remember to use ti [latex](\uparrow\hat{7})[/latex], not te [latex](\downarrow\hat{7})[/latex], to build the leading-tone chord. In other words, remember to raise the leading tone.
- In major, the leading-tone seventh chord’s quality is half diminished if we don’t alter it (e.g. in C major: B-D-F-A). Composers tend to prefer the sound of a fully diminished 7th chord, though, so we nearly always find that in major keys, composers lower the chordal seventh to make the chord fully diminished (e.g., in C major: B-D-F-A♭) ( ). You can use both, but viio7 is much more common than vii∅7, and we’ll see why below.
https://musescore.com/user/32728834/scores/6245147/embed
Substituting the leading-tone chord in place of V(7)
Almost all inversions of [latex]\mathrm{vii^{o7}}[/latex] (plus [latex]\mathrm{vii^{o6}})[/latex] can substitute for an inversion of [latex]\mathrm{V^7}[/latex] (and [latex]\mathrm{V