IV. Diatonic Harmony, Tonicization, and Modulation
56
John Peterson
Key Takeaways
- This chapter discusses the predominant seventh chords ii7, IV7, vi7, and iii7.
- ii7 and its inversions are the most common predominant seventh chord, and Example 2 shows which inversions of ii7 are more common than others.
- When writing with predominant seventh chords, two general principles apply with respect to the treatment of the chordal seventh:
- Approach the chordal seventh by step or common tone.
- Resolve the chordal seventh down by step.
Earlier, we saw how adding a chordal seventh to the dominant strengthened its drive toward the tonic. In this chapter, we see that something similar can be accomplished by adding a chordal seventh to predominant chords: it can intensify their motion to the dominant (Example 1). Adding a seventh to ii chords is common; it also occurs with the other predominant chords (particularly IV and vi), but less frequently. All predominant seventh chords share two general guidelines for the treatment of a chordal seventh:
- The chordal seventh is usually approached by step or common tone.
- The chordal seventh resolves down by step.
https://musescore.com/user/32728834/scores/6260230/embed
Example 1. A predominant seventh chord in Josephine Lang, “Dort hoch auf jenem Berge”
Adding a chordal seventh to ii
Example 2 lists the various inversions of ii7 from more common to less common. We’ll discuss each in turn.
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Example 2. Inversions of ii7 sorted by relative degree of commonality.
ii[latex]^6_5[/latex]
[latex]\mathrm{ii^6_5}[/latex] often substitutes for [latex]\mathrm{ii^6}[/latex], meaning that it commonly shows up near the end of a phrase (Example 1). Other than the typical part writing procedures and treatment of the chordal seventh, there aren’t any new voice leading concerns when writing with [latex]\mathrm{ii^6_5}[/latex] (Example 3).
https://musescore.com/user/32728834/scores/6260497/embed
Example 3. Writing with ii[latex]\mathit{^6_5}[/latex].
ii7
ii7 is typically found near the end of a phrase (Example 1). In addition to following typical writing procedures and treatment of the chordal seventh, there are two main issues to be aware of when writing with ii7:
- The chord is often preceded by tonic, and it’s best to use I6 rather than I to avoid potential parallels,
- When ii7 resolves to V7, either ii7 or V7 will need to be incomplete to avoid causing a voice-leading problem (Example 4).
https://musescore.com/user/32728834/scores/6260500/embed
Example 4. Writing with ii7.
ii[latex]^4_2[/latex]
[latex]\mathrm{ii^4_2}[/latex] typically expands tonic at the beginning of a phrase in the progression [latex]\mathrm{I-ii^4_2-V^6_5-I}[/latex] (Example 5). This progression is easy to write if you follow the typical writing procedure and treatment of the chordal seventh.
https://musescore.com/user/32728834/scores/6260504/embed
Example 5. Writing with ii[latex]\mathit{^4_2}[/latex].
ii[latex]^4_3[/latex]
[latex]\mathrm{ii^4_3}[/latex] is relatively uncommon. When it does show up, it’s usually in place of a strong predominant at a phrase ending (Example 6). Other than following the typical writing procedure and treatment of the chordal seventh, there isn’t anything new to learn about voice leading.
https://musescore.com/user/32728834/scores/6260506/embed
Example 6. Writing with ii[latex]\mathit{^4_3}[/latex].
Other predominant sevenths
The remaining predominant sevenths, IV7, vi7, and iii7 are not nearly as common as ii7 and its inversions. Among them, IV7 and vi7 are more common than iii7, which makes sense given that [latex]\mathrm{iii}[/latex] as a triad isn’t very common in the first place. Both IV7 and vi7 tend to show up as root-position chords when they’re used, and vi7 only shows up as a harmony connecting the tonic area to the strong predominant area, and not as part of a deceptive motion (in other words, V7 to vi7 is not common). Example 7 shows sample voice leading involving these chords. It follows typical writing procedures and treatment of chordal sevenths.
https://musescore.com/user/32728834/scores/6260511/embed
Example 7. Writing with IV7 and vi7.
Altered dominant chords
Altered dominant chords feature either an augmented or diminished fifth. Augmented fifths are indicated in analysis by “+” beside the Roman numeral. Diminished fifths are indicated by a “o” beside the Roman numeral.
Dominant with an augmented fifth
If you raise the fifth of a dominant triad, it will become an augmented triad. Typically, raised fifths resolve upward by step to the third of its target chord. Note that the augmented triad is a symmetrical chord than can be interpreted in multiple ways, making it difficult to identify its root without proper surrounding context. Like the diminished-seventh chord, this means that the augmented triad can be a pathway to distant, chromatic modulations. See Example 1, which shows the three possible enharmonic interpretations and resolutions of the C augmented triad.
Importantly, these chords do not resolve easily to minor triads, since the augmented fifth would not be able to resolve upward by step.
Example 1: The three possible resolutions of the C augmented triad.
The Dominant with Diminished Fifth
When you add a 7th to a Vo chord, you get a chord that sounds precisely like a French augmented-sixth chord. This equivalence becomes even clearer when you use the Vo7 chord in second inversion, leaving the lowered fifth in the bass voice to resolve downward by step. As Example 2 shows, the chords Vo4/3/V and the French augmented-sixth chord are identical.
Example 2: The dominant chord with a diminished fifth, and its equivalence with the French augmented-sixth chord.
Extended dominant chords
Extensions can be added to dominant chords to create new and interesting sonorities. These chords are typically found only in root position.
When composing these chords in a four-voice texture, you need to decide which notes to leave out. These chords will always include the root and the chordal seventh.
The V9 chord replaces a doubled root with a ninth. The ninth should resolve down by step.
The V11 chord replaces the third with an eleventh. The eleventh “resolves” by common-tone. This chord typically includes both the ninth and the eleventh, and resembles a IV chord with scale-degree 5 in the bass.
The V13 chord replaces the fifth with a thirteenth. The thirteenth “resolves” by leaping down by third to scale-degree 1.
- Coming soon!
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