IV. Diatonic Harmony, Tonicization, and Modulation
IV. Diatonic Harmony, Tonicization, and Modulation
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John Peterson
Key Takeaways
- Prolongation is a common feature of phrase beginnings in Western classical music.
- The most common way to prolong the tonic is by alternating tonic with V6 or inverted V7 chords.
Overview
Phrase beginnings in Western classical music typically feature a prolongation of tonic harmony to establish the home key. “Prolongation” just means that the harmony’s influence lasts longer than a single chord. Say, for example, that you bought a serving of ice cream that you wanted to enjoy over an extended period. One way to do it would be to take small bites to extend the length of time you’re eating. While this method would work, you might be eating ice cream soup by the end. Another way to do it would be to eat some, put it in the freezer, do some other activity, then come back and eat some more. You might say, “I’ve been eating ice cream all day,” even though you haven’t literally been eating ice cream every second of the day (as much as you might want to).
Something analogous happens in music. We could prolong the tonic’s importance at the beginning of a phrase by holding or repeating the chord (like taking small bites of the ice cream), as in
, but more interesting and rewarding is to use other chords between instances of the tonic (like putting the ice cream in the freezer and coming back to it later).https://musescore.com/user/32728834/scores/6240782/embed
shows one instance of the most common way to prolong tonic at the beginning of a phrase: using inverted V7s between tonic triads. The tonic’s influence is felt more strongly because (1) it’s on stronger beats or hyperbeats than the V7, and (2) it appears at least once in root position, whereas the V7 is in a weaker inversion.
https://musescore.com/user/32728834/scores/6240788/embed
Writing Tonic Prolongations
The tonic prolongations covered in this chapter are the ones most commonly seen in Western classical music, and they all share several traits:
- They are three chords long
- The first and last chords are I or I6
- The middle chord is V6 or an inverted V7
- The V6 or inverted V7 resolves using the same principles we learned in Strengthening Endings with Cadential [latex]^6_4[/latex]
Prolonging with V6/5 and V6
[latex]\mathrm{V}^6_5[/latex] typically prolongs root position I in the progression [latex]\mathrm{I-V^6_5-I}[/latex] (typical writing procedure.
). This is because ti ([latex]\hat{7}[/latex]) is in the bass, and we know that ti ([latex]\hat{7}[/latex]) must resolve to do ([latex]\hat{1}[/latex]). As always, follow thehttps://musescore.com/user/32728834/scores/6240806/embed
It’s also possible to prolong tonic with V6 rather than [latex]\mathrm{V}^6_5[/latex], though this is less common (
).https://musescore.com/user/32728834/scores/6243345/embed
Prolonging with V4/2
[latex]\mathrm{V}^4_2[/latex] usually helps us move from root position to first inversion I in the progression [latex]\mathrm{I-V^4_2-I^6}[/lat