AP Music Theory Unit 7 Secondary Function: Applied Chords, Tendency Tones, and Key Change

Secondary Dominant Chords

What a secondary dominant is

A secondary dominant (also called an applied dominant) is a dominant-function chord that briefly treats a diatonic chord (something already in the key) as if it were a temporary tonic. In other words, you “borrow” the sound of a different key for a moment to make a target chord sound more important and more strongly directed.

In a diatonic major or minor key, the dominant chord (V or V7) has a very specific job: it points to I (or i) with strong pull because it contains tendency tones—especially the leading tone (scale degree 7) that resolves up to the tonic (scale degree 1). A secondary dominant uses the same idea but aims that pull at a chord other than the main tonic.

So instead of V resolving to I, you might get:

• V/V resolving to V (a dominant of the dominant)
• V/ii resolving to ii
• V/vi resolving to vi

The slash is read “of.” V/V means “V of V” (the dominant chord in the key of the dominant).

Why secondary dominants matter

Secondary dominants are one of the main ways tonal music creates forward motion without fully changing key. They intensify a harmony that might otherwise sound routine—like ii or V—by giving it its own “mini-dominant” setup. This is a big part of how composers create direction across a phrase: you hear a stronger chain of cause-and-effect rather than a simple loop of diatonic chords.

In AP Music Theory, secondary dominants matter because you’re expected to:

• Identify and label them correctly in Roman numerals
• Spell them with correct accidentals (because they are usually chromatic)
• Resolve them correctly in voice leading (especially in SATB writing)
• Distinguish them from actual modulations (a secondary dominant typically implies tonicization, not a new key)

How secondary dominants work (the mechanism)

A secondary dominant is built exactly like a real dominant: it is a major triad (V) or a major-minor seventh chord (V7) that contains a leading tone to its target.

Step 1: Choose the target chord (the chord being tonicized)

In a given key, pick a diatonic chord that can plausibly act like a temporary tonic. In common-practice style, the most common targets are:

• V (very common)
• ii
• vi
• iii (less common)

You generally do not tonicize vii° (because it’s diminished and unstable), and tonicizing IV is less common as a secondary dominant in strict chorale style (though it happens in repertoire).

Step 2: Pretend the target chord is “I” of a temporary key

If you tonicize V in C major, you temporarily hear G major as though it were a tonic.

Step 3: Build V (or V7) in that temporary key

In the temporary key of G major, the dominant is D major (D–F#–A) and the dominant seventh is D–F#–A–C.

Notice what happened: F# is not in C major, so the secondary dominant introduces a chromatic accidental.

Step 4: Resolve like a dominant

The essential voice-leading idea is the same as V7 to I:

• The temporary leading tone resolves up by step into the target chord.
• If it’s a seventh chord, the chordal seventh resolves down by step.

Common secondary dominants in major (with a concrete map)

It helps to think: “To find V/x, build a perfect fifth above the root of x.”

Here are common secondary dominants in C major:

A key misconception: you do not label these as “II” or “III” just because they’re major. The label must show function relative to the main key, not just chord quality. For example, D major in C major is not “II” in typical AP Roman numeral usage; it is V/V because it functions as a dominant to V.

Secondary dominants in minor (extra care with scale degrees)

Minor keys already have variable scale degrees (especially 6 and 7), and the dominant in minor is typically raised (harmonic minor practice). Secondary dominants in minor can therefore create accidentals that stack on top of the minor-key alterations.

Example: A minor tonicizing V (E major).

• The target chord is V (E major is already the dominant in minor).
• V/V would be B major (B–D#–F#) resolving to E.

Here, D# and F# are chromatic in A minor.

A common mistake is to “overcorrect” by forcing everything into the natural minor collection. In tonal harmony, dominant function often implies raised leading tones, and secondary dominants are built to create that leading-tone pull.

Figured bass and inversion labeling

Secondary dominants are labeled like any other chord with inversion figures. The slash label stays the same; the figures describe inversion.

For example:

• V6/5/V = a V7 of V in first inversion
• V4/3/ii = a V7 of ii in second inversion
• V6/V = a V triad of V in first inversion

If you’re writing in SATB, inversions matter because they help you control:

• which voices get the tendency tones
• how smooth the bass line is
• whether parallel fifths/octaves appear

Voice-leading tendencies (what must resolve, and how)

Secondary dominants contain tendency tones aimed at the temporary tonic (the target chord).

In a secondary V7

• The temporary leading tone (scale degree 7 of the temporary key) resolves up by step into the root of the target chord.
• The chordal seventh resolves down by step.

Example in C major: V7/V is D7 (D–F#–A–C) resolving to G (G–B–D).

• F# (temporary leading tone in G) resolves to G.
• C (the seventh of D7) resolves to B.

A frequent part-writing error is to treat the accidental as “just a color tone” and fail to resolve it correctly. In AP-style voice leading, the chromatic tendency tone is usually the whole point.

Worked examples (analysis and spelling)

Example 1: Identify V/V in C major

Progression: C major → D7 → G major → C major

• C major is I.
• D7 is not diatonic in C (it contains F#). It resolves to G.
• Because D7 resolves to V, it is V7/V.

Roman numerals:

• I → V7/V → V → I

Example 2: Spell V/ii in G major

In G major, ii is A minor. The dominant of A is E.

So V/ii is E major (or E7) and must include G# (the temporary leading tone to A).

• V/ii (triad): E–G#–B
• V7/ii: E–G#–B–D

Resolution: V/ii resolves to ii (A minor), typically A–C–E.

What goes wrong (common misconceptions built into the concept)

1. Confusing “chromatic chord” with “secondary dominant.” Not every chord with an accidental is a secondary dominant. To qualify, it must function like V (or V7) of some diatonic target and resolve accordingly.
2. Labeling by appearance instead of function. A major chord built on scale degree 2 in a major key is often V/V, not “II.” The correct label comes from where it resolves.
3. Forgetting the resolution requirements of the seventh. If you write V7/x, the seventh should usually resolve down by step, even though the chord is “secondary.”

Exam Focus

• Typical question patterns
  • Identify and label secondary dominants in a Roman numeral analysis, often including inversion figures (e.g., V6/5/V).
  • Write or complete a four-part progression that includes a secondary dominant and resolves it correctly.
  • Multiple-choice questions that ask which chord best intensifies a move to a given diatonic harmony (e.g., “Which chord tonicizes vi?”).
• Common mistakes
  • Using the wrong accidental because you built the chord in the home key instead of the temporary key.
  • Mislabeling (e.g., calling D major “II” in C major) instead of showing secondary function (V/V).
  • Incorrect resolution of the temporary leading tone or the chordal seventh in SATB.

Secondary Leading-Tone Chords

What a secondary leading-tone chord is

A secondary leading-tone chord is a leading-tone-function chord that tonicizes a diatonic chord other than the tonic. It is most commonly written as vii°/x (a diminished triad) or viiø7/x or vii°7/x (a seventh chord) and it resolves to the target chord (x).

Just like a diatonic vii° in a key intensifies motion to I, a secondary leading-tone chord intensifies motion to some other diatonic harmony by placing a diminished chord a half step below the target’s root.

Why it matters

Secondary leading-tone chords are closely related to secondary dominants:

• Both tonicize a target chord.
• Both introduce chromatic accidentals.
• Both have strong, directed voice leading.

In many contexts, they are interchangeable in function with secondary dominants, and AP tasks often expect you to recognize that they are two different ways to create the same pull.

They also appear frequently in four-part writing because they can produce smoother bass motion than a secondary dominant. For example, instead of using V/V (D) to go to V (G), you can use vii°/V (F#°) to go to G—bass can move by step (F# to G) rather than by fifth (D to G).

How secondary leading-tone chords are constructed

A leading-tone triad is built on the leading tone of the temporary key (scale degree 7 of the tonicized chord’s key) and is diminished.

Step-by-step build process

1. Choose the target chord x (a diatonic chord in the main key).
2. Treat x as a temporary tonic.
3. Find the leading tone in that temporary key (a half step below the root of x).
4. Build a diminished triad (or seventh chord) on that leading tone.

Example: vii°/V in C major

• Target is V (G).
• Temporary key is G major.
• Leading tone to G is F#.
• Build a diminished triad on F#: F#–A–C.

That chord is vii°/V, and it resolves to G major (V).

Seventh-chord qualities: viiø7 vs vii°7

In common-practice harmony:

• A half-diminished seventh chord (viiø7) has a diminished triad plus a minor seventh above the root.
• A fully diminished seventh chord (vii°7) has a diminished triad plus a diminished seventh above the root.

Which one you get depends on the scale collection implied by the temporary key (and, in minor, whether scale degree 6 is raised). In AP Music Theory, you don’t need to “guess”—you spell what the voice leading and accidentals demand.

Example in C major, viiø7/V on F#:

• F#–A–C–E (E is a minor seventh above F#)
  This is half-diminished.

Example where fully diminished can arise is when the seventh above the leading-tone root is lowered (creating a diminished seventh), often in minor-key contexts with raised leading tone and lowered sixth in the relevant collection.

Resolution and voice leading (the real reason these chords exist)

Secondary leading-tone chords behave like intensified dominant function. Their notes are packed with tendency:

• The root of vii°/x (the temporary leading tone) resolves up by step to the root of x.
• Other chord members usually resolve by step into chord tones of the target.
• If it’s a seventh chord, the chordal seventh typically resolves down by step.

Because the chord is diminished, doubling rules matter a lot in SATB.

Doubling guidelines (typical AP-style practice)

• For a diminished triad (vii°/x), you typically double the third of the chord rather than the root (doubling the leading tone is unstable and often creates voice-leading problems).
• For seventh chords (viiø7/x or vii°7/x), you often avoid doubling altogether because seventh chords normally appear with four distinct chord members.

These are guidelines, not magical laws, but they match the style expectations in AP free-response part writing.

Comparing secondary dominants vs secondary leading-tone chords

They often serve the same harmonic goal (tonicize x), but they differ in structure and bass motion.

Worked examples

Example 1: Analyze a tonicization using vii°/ii in D major

Key: D major. Target chord ii is E minor.

• Leading tone to E is D#.
• Build diminished triad: D#–F#–A.

So D#° is vii°/ii, resolving to ii (E minor: E–G–B).

If you see the progression: A7 → D#° → Em, it can be tempting to think “we changed keys.” But if it quickly returns to D major and the cadence remains in D, it is better understood as tonicization of ii.

Example 2: Use viiø7/V instead of V7/V in C major

To tonicize V (G):

• V7/V would be D–F#–A–C.
• viiø7/V would be F#–A–C–E.

Both intensify the arrival on G, but viiø7/V gives you bass F# → G, a very clear half-step pull.

What goes wrong (and why)

1. Labeling vii°/x when the chord doesn’t resolve to x. These chords are defined by function; if it doesn’t resolve as expected, consider other explanations (passing diminished chord, common-tone diminished, or a modulation).
2. Spelling the chord with the wrong leading tone. If the chord is vii°/V in C major, the root must be F#, not F natural, because it has to be a half step below G.
3. Doubling the leading tone in a diminished triad. This frequently creates exposed octaves or unresolved tendency tones in part writing.

Exam Focus

• Typical question patterns
  • Roman numeral analysis that includes secondary leading-tone sevenths (e.g., viiø7/V) and asks for correct inversion figures.
  • Part-writing tasks that require you to resolve a vii°/x chord to its target with correct tendency-tone motion.
  • Multiple-choice listening/score questions where you identify the chromatic chord that leads into a diatonic harmony.
• Common mistakes
  • Writing a diminished chord but labeling it as V/x (or vice versa) without checking chord quality and root.
  • Misspelling accidentals (especially in minor) so the chord no longer functions as a leading-tone chord.
  • Treating vii°7 and viiø7 as interchangeable without spelling the correct chordal seventh.

Modulation

What modulation is (and how it differs from tonicization)

A modulation is a change of key that is established as a new tonal center. In contrast, tonicization is a brief emphasis of a chord through secondary function without fully establishing a new key.

This distinction is crucial in AP Music Theory because secondary dominants and secondary leading-tone chords are often the tools that make tonicizations and modulations possible—but the analysis label depends on whether the music truly “arrives” in a new key.

A practical way to think about it:

• Tonicization: “We visited another key’s dominant behavior for a moment, but we didn’t move in.”
• Modulation: “We moved in—there’s a new tonic, confirmed by cadences and harmonic context.”

Why modulation matters in this unit

Unit 7 focuses on secondary function, and modulation is the natural extension: if you can tonicize a chord, you can often turn that tonicization into a real key change by extending it, confirming it with a cadence, and reinterpreting chords in the new key.

On AP tasks, modulation shows up when you must:

• Identify the new key from accidentals and cadential confirmation
• Describe how a composer gets there (often via a pivot chord or a secondary dominant)
• Use correct Roman numerals before and after the change (sometimes with a pivot chord labeled in both keys)

How you can tell a modulation has happened

There isn’t one single “rule,” but several strong signals together.

1. Cadential confirmation

A modulation is most convincingly established by a cadence in the new key—often an authentic cadence (V to I) or a strong dominant arrival (V7 to I) that sounds like a point of arrival rather than a passing event.

If you only hear one secondary dominant resolving quickly back into the original key’s flow, that’s usually tonicization.

2. Persistence of the new key’s accidentals

A single chromatic accidental can simply be a secondary function chord. But if the new accidentals keep appearing consistently (especially leading tones and dominant-function harmonies of the new key), the music may be re-centering.

3. Reinterpretation of function

In a modulation by pivot chord, a diatonic chord can “belong” to both keys. When the same chord begins to behave according to the new key (for example, it starts acting like ii in the new key and is followed by V and I in that key), you’ve crossed from tonicization into modulation.

Common modulation types you should recognize

Pivot-chord modulation (common-chord modulation)

A pivot chord is a chord that is diatonic in both the original key and the destination key. The composer uses it as a hinge: it first makes sense in the old key, then is reinterpreted in the new key.

How it works (step-by-step):

1. Start in the original key with clear diatonic function.
2. Introduce a chord that can be analyzed in both keys (the pivot).
3. Follow it with harmonic motion that belongs clearly to the new key (often including V or vii° in the new key).
4. Confirm the new key with a cadence.

Example: C major modulating to G major (pivot chord = Am)

• In C major, A minor is vi.
• In G major, A minor is ii.

A possible progression:

C: I → vi → ii6 → V → I

If we reinterpret:

• The vi chord (Am) can become ii in G.
• Then a D (or D7) appears, functioning as V (or V7) in G.
• Arriving on G with cadential weight confirms G major.

In an analysis, the pivot chord is sometimes labeled with both Roman numerals (old key function and new key function), depending on the teacher’s and exam’s conventions. The important skill is that you can explain why it belongs to both keys and how the surrounding chords reveal the change.

Direct modulation (phrase modulation)

A direct modulation changes key without a pivot chord—often at a phrase boundary. You might end a phrase in one key and begin the next phrase in another, sometimes using a dominant in the new key right away.

This is common in simpler textures where a “common chord” isn’t emphasized. What makes it feel like modulation is the immediate and clear establishment of the new tonic (often through V to I).

Common-tone modulation (conceptual awareness)

In some repertoire, a composer holds one pitch constant (a common tone) while harmonies around it shift, helping your ear accept a new key. In AP-level analysis, you’re more commonly asked about pivot-chord approaches, but it’s still useful to recognize that composers can use shared tones as a bridge.

How secondary function relates to modulation

Secondary dominants and secondary leading-tone chords can be the “doorway” into a modulation.

• In C major, V/V (D major or D7) is a secondary dominant if it resolves to V and then returns to C.
• But if that D7 leads to G and the music continues with predominant and dominant function in G (like Am as ii, then D7 as V7, then G as I), the earlier V/V can be reinterpreted as simply V7 in the new key of G.

This is one reason exam questions sometimes feel tricky: the same chord (like D7) can be heard as:

• V7/V in C major (tonicization)
• V7 in G major (after modulation)

The musical context decides.

Worked modulation examples (with analysis logic)

Example 1: Is it tonicization or modulation?

Progression (chords): C → D7 → G → C

• D7 is V7/V in C.
• It resolves to G (V), but then immediately returns to C.
• There is no cadential confirmation in G as a new tonic.

Conclusion: tonicization of V, not modulation.

Example 2: Pivot-chord modulation C major to G major

Progression (one possible realization):

C: I → vi → ii → V7 → I

Reinterpreting for modulation:

• Start: C major is clear at I.
• vi (Am) is pivot: vi in C, ii in G.
• Next chord D7 strongly suggests G major (it’s V7 in G).
• Then G arrives with cadential weight.

Analysis approach you could write:

• C major: I → vi (pivot)
• G major: ii → V7 → I

The key is that the harmony after the pivot behaves like G major long enough to feel established.

Example 3: Modulation in minor using secondary function as a setup

Imagine E minor moving toward G major (relative major). A composer might introduce D# (leading tone to E) for a strong dominant in E minor, then shift toward F# leading tone to G (F# is diatonic in G major) and confirm G with a cadence.

Even if you don’t see the whole texture, the analytical skill is the same: track which leading tones and dominants are being emphasized, and look for a cadence that “locks in” the new tonic.

What goes wrong when students analyze modulation

1. Calling every secondary dominant a modulation. A single V/V is not enough. Look for a broader change in harmonic function and cadential confirmation.
2. Choosing the new key solely from one accidental. Accidentals can be borrowed tones, chromatic passing tones, or applied-chord tones. Confirm with dominant-to-tonic behavior.
3. Losing track of Roman numeral frame of reference. Once the key changes, Roman numerals must be re-centered to the new tonic. Students often keep analyzing in the old key even after a clear new cadence.

Exam Focus

• Typical question patterns
  • Identify whether a passage tonicizes a chord or modulates to a new key, citing evidence (cadence, accidentals, functional progression).
  • Analyze a short excerpt with a pivot chord, labeling Roman numerals before and after the modulation (sometimes indicating the pivot chord’s dual function).
  • Part-writing or composition-style prompts where you must reach a new key using a pivot chord and include appropriate secondary function to smooth the transition.
• Common mistakes
  • Declaring a modulation without a convincing cadence or sustained harmonic context in the new key.
  • Misidentifying the pivot chord (picking a chord that is not actually diatonic in both keys).
  • Forgetting that secondary dominants/leading-tone chords often introduce the leading tone of the temporary key, not the home key, so the accidental must match the intended destination.