IV. Diatonic Harmony, Tonicization, and Modulation

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.

Chapter Playlist


Phrase beginnings in Western classical music typically feature a 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 Example 1, 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).

Example 1. Prolongation by sustaining or repeating a chord.

Example 2 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.

Example 2. Tonic prolongation in Clara Schumann, Piano Trio, III, mm. 1–2 (0:00-0:08).

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:

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] (Example 3). 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 the .

Example 3. Tonic prolongation involving [latex]\mathit{V^6_5}[/latex].

It’s also possible to prolong tonic with V6 rather than [latex]\mathrm{V}^6_5[/latex], though this is less common (Example 4).

Example 4. Tonic prolongation involving [latex]\mathit{V^6}[/latex].

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}[/latex] (Example 5). This is because [latex]\mathrm{V}^4_2[/latex] has fa ([latex]\hat{4}[/latex]) in the bass, which must resolve to mi ([latex]\hat{3}[/latex]) since fa ([latex]\hat{4}[/latex]) is the chordal seventh. Again, follow the .

Example 5. Tonic prolongation involving [latex]\mathit{V^4_2}[/latex].

Prolonging with V4/3

Most commonly, [latex]\mathrm{V}^4_3[/latex] helps us move from root position to first inversion I in the progression [latex]\mathrm{I-V^4_3-I^6}[/latex] (Example 6). It occasionally prolongs root position tonic in the progression [latex]\mathrm{I-V^4_3-I}[/latex], but this isn’t very common (Example 7). These options are available because [latex]\mathrm{V}^4_3[/latex]’s bass note, re ([latex]\hat{2}[/latex]), may go either to do ([latex]\hat{1}[/latex]) or to mi ([latex]\hat{3}[/latex]). Again, follow the .

Example 6. Tonic prolongation involving [latex]\mathit{V^4_3}[/latex].

Example 7. Less common tonic prolongation involving [latex]\mathit{V^4_3}[/latex].

Writing with [latex]\mathrm{V}^4_3[/latex] also offers one exception to the rule that the chordal seventh, fa ([latex]\hat{4}[/latex]), must resolve down (Example 8). Here, fa moves up to sol ([latex]\hat4-\hat5[/latex]). This exception is made possible because the bass creates parallel tenths with the upper voice that takes the line mifasol ([latex]\hat3-\hat4-\hat5[/latex]).

Example 8. Exception to the typical resolution of the chordal seventh.

Combining Progressions

By chaining together several of these tonic prolongation progressions, composers can extend the tonic’s influence for quite a while at the beginning of a phrase, as in Example 2. A part-written example is given in Example 9.

Example 9. Extensive tonic prolongation.

Bass Line Summary

A summary of the four tonic-prolongation bass lines discussed in this chapter, along with their associated progressions, is given in Example 10.

[table id=42 /]

Example 10. Summary of bass lines and their associated tonic prolongation progressions.

  1. Prolonging Tonic at Phrase Beginnings with V6 and Inverted V7 (.pdf, .docx, recording). Asks students to write from Roman numerals and figures and complete a guided analysis. Download score.


Icon for the Creative Commons Attribution-ShareAlike 4.0 International License

OPEN MUSIC THEORY by John Peterson is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License, except where otherwise noted.

Share This Book