IV. Diatonic Harmony, Tonicization, and Modulation

# Prolongation at Phrase Beginnings using the Leading-Tone Chord

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 V^{7}: the . shows a passage from Mozart’s “Agnus Dei” that uses vii^{o7} 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 V^{7} 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.

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 vii
^{o6}. 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 7
^{th}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 vii^{o7}is much more common than vii^{∅7}, and we’ll see why below.

# 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^6})[/latex] according to which note is in the bass (

). What this means is that, for example, [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. Similarly, [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], and [latex]\mathrm{vii^{o}\begin{smallmatrix}4\\3\end{smallmatrix}}[/latex] can be used in place of [latex]\mathrm{V^4_2}[/latex].

Bass note | [latex]\mathrm{V}^{7}[/latex] | [latex]\mathrm{vii}^{\circ7}[/latex] |
---|---|---|

ti ([latex]\hat{7}[/latex]) | [latex]\mathrm{V}\begin{smallmatrix}6\\5\end{smallmatrix}[/latex] | [latex]\mathrm{vii}^{\circ7}[/latex] |

re ([latex]\hat{2}[/latex]) | [latex]\mathrm{V}\begin{smallmatrix}4\\3\end{smallmatrix}[/latex] | [latex]\mathrm{vii}^{\circ}\begin{smallmatrix}6\\(5)\end{smallmatrix}[/latex] |

fa ([latex]\hat{4}[/latex]) | [latex]\mathrm{V}\begin{smallmatrix}4\\2\end{smallmatrix}[/latex] | [latex]\mathrm{vii}^{\circ}\begin{smallmatrix}4\\3\end{smallmatrix}[/latex] |

Luckily, there isn’t too much else to learn with respect to part writing. Continue to follow and to resolve active notes in the upper voices according to their tendencies. *le*/*la* [latex](\downarrow\hat{6}[/latex]/[latex]\hat{6})[/latex]. shows tonic prolongations involving vii^{o7} and its inversions, and it compares each to a corresponding prolongation involving [latex]\mathrm{V^7}[/latex] and its inversions.

Active note | Resolution |
---|---|

ti ([latex]\hat{7}[/latex]) | do ([latex]\hat{1}[/latex]) |

re ([latex]\hat{2}[/latex]) | do ([latex]\hat{1}[/latex]) |

fa ([latex]\hat{4}[/latex]) | mi ([latex]\hat{3}[/latex]) |

le/la ([latex]\downarrow\hat{6}[/latex]/[latex]\hat{6}[/latex]) | sol ([latex]\hat{5}[/latex]) |

# vii^{o}4/2

You might have noticed that [latex]\mathrm{vii^{o}\begin{smallmatrix}4\\2\end{smallmatrix}}[/latex] doesn’t correspond to an inversion of [latex]\mathrm{V^7}[/latex]. That’s because it’s built on *le* [latex](\downarrow\hat{6})[/latex], which isn’t in [latex]\mathrm{V^7}[/latex]. [latex]\mathrm{vii^{o}\begin{smallmatrix}4\\2\end{smallmatrix}}[/latex] is a very rare harmony because the expected resolution from *le* down to *sol* [latex](\downarrow\hat6-\hat5)[/latex] (see ) occurs in the bass. So far, we’ve seen that *sol* [latex](\hat{5})[/latex] in the bass typically supports V or [latex]\mathrm{V^7}[/latex], and that’s also the case here: [latex]\mathrm{vii^{o}\begin{smallmatrix}4\\2\end{smallmatrix}}[/latex] goes to [latex]\mathrm{cad.^6_4}[/latex] ( ). Again, though, [latex]\mathrm{vii^{o}\begin{smallmatrix}4\\2\end{smallmatrix}}[/latex] is not a very common chord.

# Using the leading-tone chord as a half-diminished seventh chord

vii^{∅7} presents voice-leading challenges that are not present with vii^{o7} because it contains a perfect fifth between *re* [latex](\hat{2})[/latex] and *la* [latex](\hat{6})[/latex]. This is perhaps another reason that composers favor vii^{o7} over vii^{∅7}: with ∅7, we need to watch out for parallel fifths, as in An easy way to avoid them is to always make sure that *re* [latex](\hat{2})[/latex] is above *la* [latex](\hat{6})[/latex] when you use vii^{∅7} or its inversions. The one time where this advice is impossible is with [latex]\mathrm{vii^{∅}\begin{smallmatrix}6\\5\end{smallmatrix}}[/latex], where *re* [latex](\hat{2})[/latex] is in the bass. Although it’s possible to avoid parallels with [latex]\mathrm{vii^{∅}\begin{smallmatrix}6\\5\end{smallmatrix}}[/latex], we’d recommend just using [latex]\mathrm{vii^{o}\begin{smallmatrix}6\\5\end{smallmatrix}}[/latex] or expanding I^{6} (as shown below) instead.

- Prolongation at Phrase Beginnings using the Leading-tone Chord (.pdf, .docx). Asks students to write from Roman numerals, complete analysis, and realize figured bass.

The triad or seventh chord built on *ti* (7̂).

1. Write the entire bass

2. Write the entire soprano to make a smooth melody that interacts well with the bass. Choose active notes for the soprano above dominant-function chords, and remember you do not always need to write left to right.

3. Write the inner voices by asking, "What notes do I already have? What notes do I still need? Considering spacing and resolution, what note placement would give me the smoothest motion?"