AP Music Theory Unit 7 ReviewSecondary Function

AP Music Theory Unit 7 is about tonicization, the trick of making a chord that isn't the tonic sound like a temporary tonic without actually changing keys. The biggest idea is that you can put any major or minor triad in the spotlight by preceding it with its own dominant (a secondary dominant like V7/V) or its own leading-tone chord (like vii°7/V). These chords bring chromatic notes into your analysis and part writing for the first time in the course, and they follow the same resolution rules you already know from regular V and vii° chords.

What this unit covers

Tonicization, the core concept

• The key a piece starts and ends in is its tonic or primary key. Tonicization makes some other chord sound like "home" for a moment, but the primary key never changes.
• Tonicization is fleeting. It lasts a chord or two and never gets a real cadence in the new key. If the music cadences and settles in the new key, that's modulation, which is a different process.
• Any major or minor triad in the key can be tonicized. Diminished triads cannot, because a diminished chord can't sound like a tonic.
• You hear tonicization as a quick "pull" toward a non-tonic chord, usually signaled by an accidental that doesn't belong to the key.

Secondary dominant chords

• A secondary dominant is the dominant of a chord other than the tonic. V/V (read "five of five") is the dominant of the dominant. In C major, V/V is a D major triad, which needs an F sharp.
• The label format is always function/target. V7/IV, V/vi, V7/ii all follow the same logic. The chord after the slash is the temporary tonic.
• The chromatic alteration usually creates a temporary leading tone, a note a half step below the root of the target chord. That half-step pull is what makes the target feel like a tonic.
• The most common melodic clue is raised scale degree 4 moving up to scale degree 5. When you see or hear sharp 4 going to 5, suspect a tonicization of V.
• Secondary dominants can appear as triads (V/x) or seventh chords (V7/x), and in inversions, just like regular dominants.

Secondary leading-tone chords

• These are diminished triads and diminished seventh chords built on the leading tone of the chord being tonicized. vii°7/V tonicizes V the same way vii°7 tonicizes I.
• They come in three flavors: the diminished triad (vii°/x), the fully diminished seventh (vii°7/x), and the half-diminished seventh (viiø7/x).
• The root of the chord sits a half step below the root of the target chord, so the resolution up by half step is built into the spelling.
• They're also called applied leading-tone chords or applied diminished seventh chords. "Applied" and "secondary" mean the same thing here.

Part writing with secondary function chords

• The big rule is that nothing new is required. A secondary dominant follows every doubling and voice-leading rule of a regular dominant, and a secondary leading-tone chord follows every rule of a regular leading-tone chord.
• Chordal sevenths still resolve down by step. The temporary leading tone resolves up by step to the root of the target chord (in outer voices especially).
• Don't double the temporary leading tone. Doubling it forces parallel octaves or an unresolved tendency tone.
• When you write a bass line under a given soprano, chromatic pitches in the melody hint at tonicization. A sharp 4 to 5 in the soprano often implies V/V to V underneath.
• Avoid parallel fifths and octaves, exactly as in Units 4 and 5. The accidentals raise the stakes because chromatic motion makes errors easier to write.

Unit 7, Secondary Function at a glance

Why Unit 7, Secondary Function matters in AP Music

This is where chromaticism enters the course. Through Unit 6, every chord you analyzed and wrote came from the seven notes of the key. Unit 7 shows that accidentals aren't random color; they're functional, and almost every chromatic note in 18th-century style points at a temporary tonic.

• It deepens the course's central idea of harmonic function. Dominant function isn't tied to one chord; it's a relationship you can apply to any major or minor triad in the key.
• It explains the accidentals you'll see in nearly every real score, sight-singing melody, and dictation excerpt from here on.
• It's the bridge between staying in one key and leaving it. Tonicization is modulation in miniature, so getting this right makes key changes much easier to hear and label.

How this unit connects across the course

• Triad and seventh-chord quality (Unit 3) is how you spot these chords on the page. A major-minor seventh chord that isn't V, or a diminished seventh that isn't vii°7, is almost certainly a secondary function chord.
• Dominant and leading-tone resolution rules (Unit 4) transfer directly. Everything you learned about resolving V7 to I and vii° to I now applies to V7/x and vii°7/x resolving to x.
• Secondary dominants slot into the predominant-to-dominant progressions of Unit 5. V/V is essentially a souped-up predominant; it sits where ii or IV would sit and intensifies the drive to V.
• Tonicization sets up the formal analysis in Unit 8. Recognizing brief tonicizations versus real key changes is essential when you map out sections of binary and other forms.

Key notation and chord types

• V/x ("V of x"): a secondary dominant triad; the slash means "dominant of," and x names the chord being tonicized.
• V7/x: the secondary dominant seventh, the most common tonicizing chord; its chordal seventh must resolve down by step.
• V/V and V7/V: the most frequent secondary dominants; in major keys they require raised scale degree 4.
• vii°/x: a secondary leading-tone diminished triad, usually in first inversion like regular vii°.
• vii°7/x: a secondary fully diminished seventh chord; every note is a tendency tone, so resolve each by step.
• viiø7/x: the half-diminished version; less intense, but it follows the same resolution logic.
• Inversion figures on secondary chords: a label like V6/5/V works exactly like V6/5, just aimed at V instead of I.
• Accidentals in Roman numeral analysis: the chromatic note belongs to the temporary key, so spell it as the leading tone or other needed alteration of the target chord, not as a random enharmonic.

Unit 7, Secondary Function on the AP exam

Secondary function shows up across both halves of the exam. In the multiple-choice section, you'll identify tonicization in performed music (hearing the chromatic pull toward a non-tonic chord in a listening excerpt) and in notated music (spotting the accidental, naming the chord with the correct slash notation, and identifying the target). In harmonic dictation, a secondary dominant is a classic way the exam tests whether you hear function rather than just bass notes.

In the free-response section, secondary function appears in the part-writing questions. The figured-bass and Roman numeral realization FRQs regularly include a chord like V7/V or vii°7/V, and you're graded on the same things as always: correct spelling with the right accidental, the chordal seventh resolving down, the temporary leading tone resolving up, and no parallels. The composing-a-bass-line FRQ rewards you for noticing when a chromatic soprano note (like sharp 4 to 5) implies a tonicization and harmonizing it accordingly. Sight-singing melodies can include chromatic notes that arise from tonicization, so practice singing raised scale degree 4 resolving to 5.

Essential questions

• How can music make a non-tonic chord sound like home without ever leaving the primary key?
• Why do the same voice-leading rules govern V7 to I and V7/V to V?
• What does a chromatic accidental in tonal music usually signal, and how do you decide what it's pointing at?
• Where is the line between a tonicization and a true modulation?

Key terms to know

• Tonicization: making a non-tonic chord sound like a temporary tonic for a brief moment without changing the primary key.
• Primary key: the key a work starts and ends in; tonicization never displaces it.
• Secondary dominant: the dominant (V or V7) of a chord other than the tonic, labeled V/x or V7/x.
• Applied chord: another name for a secondary function chord; "applied" and "secondary" are interchangeable.
• Secondary leading-tone chord: a diminished triad or diminished seventh chord whose root is the leading tone of the chord being tonicized.
• Fully diminished seventh chord: a diminished triad plus a diminished seventh, the most intense secondary leading-tone option.
• Half-diminished seventh chord: a diminished triad plus a minor seventh, a milder alternative spelled viiø7/x.
• Temporary leading tone: the chromatically raised note a half step below the target chord's root; it must resolve up and should never be doubled.
• Target chord: the chord after the slash, the one being tonicized; it must be major or minor, never diminished.
• Chordal seventh: the seventh of any seventh chord; it always resolves down by step, including in secondary chords.
• Chromatic pitch: a note outside the key signature; in this style it usually signals tonicization.
• Modulation: an actual change of key confirmed by a cadence, in contrast to the fleeting effect of tonicization.

Common mix-ups

• Tonicization is not modulation. Tonicization is brief and never cadences in the new key. If the music cadences and stays in the new key, label it a modulation.
• V/V is not just "ii with a sharp." In C major, ii is D minor and V/V is D major. The raised third (F sharp) is what creates the leading tone to G, so leaving out the accidental destroys the function.
• You can't tonicize a diminished chord. There is no V/vii° in a major key, because vii° can never sound like a tonic.
• The slash in V7/V is not an inversion slash from lead-sheet notation. In Roman numeral analysis it means "of," so V7/V is a chord built on the dominant of the dominant, not "V7 over a V bass."