IV. Diatonic Harmony, Tonicization, and Modulation


John Peterson and Megan Lavengood

Key Takeaways

  • Tonicization is the process of making a non-tonic chord sound like a temporary tonic. This is done with chromatic chords called applied chords, or secondary dominant chords (V(7)) and secondary leading-tone chords (viio(7)) borrowed from the temporary key.
  • Applied chords are notated with a slash. The chord before the slash is the identity of the applied chord within the secondary key, and the chord after the slash is the chord being tonicized. It’s read aloud from left to right with the word “of” replacing the slash: V/ii becomes “five of two.”
  • Applied chords nearly always involve accidentals, and especially accidentals that raise the pitch.
  • Another way of thinking about applied chords is to imagine them as altered versions of the diatonic chord with which it shares a root (for example, ii becomes II♯, which is V/V).

Chapter Playlist

Tonicization is the process of making a non-tonic chord temporarily sound like tonic. It’s accomplished using secondary dominant or secondary leading-tone chords (sometimes called applied dominant and applied leading-tone chords). First, we’ll learn how to tonicize the dominant, and then we’ll see tonicizations of non-dominant chords.

Tonicizing V

Analyzing tonicization

Secondary dominant chords (V(7)/V)

Example 1 analyzes a passage that temporarily makes V sound like the tonic chord. Example 2 extracts the two chords from Example 1 that participate in the tonicization. We have a C7 chord moving to an F chord, so if we were to analyze these chords without considering the key signature or the context that Example 1 provides, we’d say the two chords represent the progression [latex]\mathrm{V^6_5-I}[/latex] in F major (Example 2a).

Example 1. Tonicization in Joseph Bologne, Six Concertante Quartets, no. 1, II, mm. 1–8.

Example 2. Reduction of the tonicization in Joseph Bologne, Six Concertante Quartets, no. 1, II, mm. 3–4.

If we now reconsider the context that Example 1 provides, we can see that the F major chord functions as V in the excerpt’s home key of B♭ major (Example 2b). Indeed, it’s the chord that creates the half cadence that ends the first phrase. We know that we haven’t changed keys here because, in addition to the half cadence being in B♭ major, the second phrase also begins in B♭ major (it repeats the beginning of the first phrase). The C7 chord, however, clearly doesn’t belong to B♭ major—that’s what the E♮ accidental in the bass tells us. As we determined in Example 2, the C7 chord is [latex]\mathrm{V^6_5}[/latex] of the F major chord. To represent that in the context of Example 1, we say that the C7 chord is “[latex]\mathrm{V^6_5}[/latex] of V,” and we write “[latex]\mathrm{V^6_5/V}[/latex].” In other words, the F major chord is V, and the C7 chord is the [latex]\mathrm{V^6_5}[/latex] of that V chord. We’ve just labeled our first secondary dominant chord!

Secondary leading-tone chords (viio(7)/V)

Tonicization can also be accomplished using secondary leading-tone chords, as in Example 3.

Example 3. Tonicization in Josephine Lang, “Du gleichst dem klaren blanen See,” mm. 21–24.

Example 4. Reduction of the tonicization in Josephine Lang.

Example 4 walks through how to understand the relationship between the two highlighted chords in Example 3.

  1. If we were in G major, we would analyze these chords as viio7–I. Recall that when we learned about the leading-tone seventh chord, we discovered that it’s common to lower the chordal seventh in major to create a fully diminished seventh chord. That’s still true here (notice the E♭!).
  2. The passage in Example 3 is in C major, so we would analyze the G major chord as V, rather than I. That means the F♯o7 chord is viio7 of the V chord. We write “viio7/V” and say “seven diminished seven of five.”
  3. The passage in Example 3 adds a [latex]\mathrm{cad.^6_4}[/latex] to embellish the dominant. That’s why the viio7/V doesn’t resolve directly to V.
  4. The [latex]\mathrm{cad.^6_4}[/latex] resolves to V7 rather than the V triad. Now we’ve arrived at the passage in Example 3.

Summary: Steps for analyzing tonicization

Note: It’s rare but possible in classical music to have a half-diminished seventh chord act as an applied chord. It’s even less common in jazz, where it’s almost certainly an applied ii∅7.

Chromaticism is an indication that tonicization may be present. Since only V(7) and viio7 (or, rarely, vii∅7—see note in sidebar) can create tonicization, one of the most helpful things for determining the label is to ask “what is the quality of the chromatic chord?” The quality determines the label: if the chord is a major triad or dominant seventh chord, it gets the label V(7). If the chord is a diminished triad or diminished seventh chord, it gets the label viio(7).

When you come across a chromatic note, stop and ask the following questions:

  1. Is the chromatic note part of the chord, or is it an embellishing tone?
    1. Part of the chord: move on to question 2
    2. Embellishing tone: label appropriately
  2. What’s the quality of the chord?
    1. Major triad or dominant seventh chord: secondary V chord; label is V(7)/x
    2. Diminished triad or diminished seventh: secondary viio chord; label is viio7/x
  3. To determine x above, ask: In what key is the chromatic chord V or viio? Then, determine what Roman numeral the tonic triad of that key would get in the home key of your passage. That Roman numeral is x.

Writing applied chords


The video in Example 5 walks through the steps for spelling V7/V, viio7/V, and vii∅7/V in major and minor keys. We recommend you grab a piece of staff paper so you can follow along by pausing the video and trying the exercises yourself. The steps are summarized below:

  1. Determine the root of the chord being tonicized
  2. Pretend this root is the tonic of a temporary key
  3. Spell the top Roman numeral in that key (either V7 or viio7)

Example 5. Steps for spelling applied chords.


The leading tone of the applied chord is referred to as the secondary leading tone; the chordal seventh is referred to as the secondary seventh. These dissonances resolve just as they normally would in their own key.

Example 6. If the applied chord is proceeding to another seventh chord, the secondary leading tone may resolve downward, instead of upward like a leading tone normally would, into the seventh of the next chord.

One exception is that when the tonicized chord is itself a seventh chord (as in the progression D7–G7–C), the secondary leading tone may resolve down by semitone into the seventh of the following chord. In the example progression, this would create a nice chromatic line: F♯–F♮–E (Example 6).

The video in Example 7 walks through the steps for spelling V7/V, viio7/V, and vii∅7/V in major and minor keys. Like with the previous video, we recommend pausing to try each exercise on staff paper. The steps are summarized below:

  1. Spell the secondary chord
  2. Follow the typical writing procedure to part-write, but think in the temporary new key to determine how tendency tones resolve
  3. Check accidentals (especially if in minor)

Example 7. Steps for resolving applied chords.


Tonicizing chords other than V


Any major or minor triad can be tonicized, not just V. Diminished and augmented triads can’t be tonicized, since there are no diminished or augmented keys. This means that every Roman numeral can be tonicized except viio and iio.

Analyzing various tonicizations

When chords other than V are tonicized, we follow the same steps for analysis that we learned earlier; the only difference is that there are now more possibilities for which chords can be tonicized. Be on the lookout for chromatic notes: these are signals that tonicization may be present!

As you might imagine, the frequency with which a given chord is tonicized is related to the frequency with which that chord generally appears. For instance, the dominant and strong predominant chords are quite common, so we also see those chords tonicized with some frequency. The vi chord, while less common than ii, IV, and V, also frequently gets tonicized. The iii and VII (minor only) chords are uncommon harmonies, and we tend not to see them tonicized frequently.

Tonicizing strong predominants

Tonicizing strong pre-dominants usually involves chromatic inflection of members of the tonic triad. For example, a tonic triad can easily be turned into a V7/IV chord by adding te [latex](\downarrow\hat7)[/latex] to the triad (Example 8). Similarly, a tonic triad can be turned into viio7/ii by raising do ([latex]\hat{1}[/latex]) and adding te [latex](\downarrow\hat7)[/latex]  (Example 9).

Example 8. Tonicizing IV in Joseph Bologne, String Quartet no. 4, I, mm. 41–47 (1:18–1:30).

Example 9. Tonicizing ii in Maria Szymanowska, Minuet no. 4, mm. 57–64 (1:48–1:55).

Tonicized deceptive motion

One striking way to use tonicization is to highlight a deceptive motion (Example 10). Here, the dominant moves to viio7/vi before the vi chord arrives, which draws our attention even more to the absence of the expected tonic after the V chord.

Example 10. Tonicized deceptive motion in Josephine Lang, “Mag da draussen Sehnee,” mm. 1–5.

Adding tonicization to diatonic progressions

The steps for part-writing tonicization remain the same as for tonicizations of V. Now, however, we should expect to see tonicizations of non-dominant major and minor triads. Example 11 shows a diatonic progression (a) to which several tonicizations have been added (b).

Example 11. Adding tonicizations to a diatonic progression.

Secondary dominants as altered diatonic chords

Another way of thinking about secondary chords is to imagine them as altered versions of the diatonic chord with which it shares a root.

The most straightforward example is when a ii chord is chromatically altered by changing fa ([latex]\hat{4}[/latex]) to fi ([latex]\uparrow\hat{4}[/latex]) and then progresses, like usual, to the dominant chord. This alteration of fa to fi [latex](\hat4-\uparrow\hat4)[/latex] turns a regular subdominant chord into a chord that has a dominant function in the key of the dominant.

Take the chord progression Dmi7–G–C in C major, which we would label with Roman numerals as ii7–V–I. If we change fa to fi ([latex]\hat4[/latex] to [latex]\uparrow\hat4[/latex], F to F♯) in the first chord, we get D7–G–C. In the key of C, we might analyze this progression as II♯7–V–I(note the uppercase Roman numeral, indicating the change of quality; the sharp sign afterward further clarifies the raised third of the chord). However, we can also note that D major belongs to G major; it is a dominant-functioning chord (V) in the key of G—the key in which the following chord is tonic. In other words, we are borrowing the dominant chord from the key of G and applying it to the G-major triad. Thus, we can re-interpret the progression as V7/V–V–I.

Practice it!

Add accidentals in the following chords to turn them into secondary dominants. What Roman numeral would you give the new chord?

Example 12 summarizes secondary chords as they relate to diatonic chords with the same root.

notation. I can become V/IV; ii can become V/V; iii can become V/vi; IV can become V/♭VII in minor only; V is already a dominant chord, so can't become a secondary dominant; vi can become V/ii in major keys only; viio can become V/iii.
Example 12. A summary of how diatonic triads may be altered chromatically to generate secondary V7 chords. Click to enlarge.
  1. Applied chords worksheet, available in three slightly different versions:
    1. Version A (.pdf, .mscx). Asks students to identify and write applied V, V7, viio, viio7, and vii∅7 chords with Roman numerals and figures.
    2. Version B—without ∅7s (.pdf, .mscz). Asks students to identify and write applied V, V7, viio, and viio7 chords with Roman numerals and figures.
    3. Version C—jazz/pop focus (.pdf, .mscz). No ∅7s or figured bass; all chords in root position. Students identify and write chord symbols in addition to notation.
  2. Tonicization Voice Leading and Score Analysis (.pdf, .docx). Asks students to write from Roman numerals and figured bass, write from a longer figured bass, and analyze a complete piece with discussion questions.

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