How does a secondary dominant briefly make another chord feel like a temporary tonic?
Topic 7.1 Tonicization through Secondary Dominant Chords: identify secondary dominants (V/V, V7/IV, and so on) and the tonicization they create.
A focused answer to AP Music Theory Topic 7.1, covering tonicization, secondary dominant chords (V/V, V7/ii and the like), how a borrowed leading tone creates a temporary tonic, reading the slash notation, and distinguishing tonicization from modulation, with a worked identification.
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What this topic is asking
The College Board (Topic 7.1) wants you to identify secondary dominant chords (V/V, V7/IV, V/ii and so on) and the tonicization they create, where a chord other than the tonic is briefly approached by its own dominant and made to feel like a temporary tonic.
Secondary dominants
To find a secondary dominant, look for a chromatic chord that is major (or a major-minor seventh) and resolves like a dominant to a diatonic chord. The chord it resolves to is the one it tonicizes.
Tonicization
The difference between tonicization and modulation is duration and confirmation: tonicization is a passing emphasis, while modulation establishes a new key with a cadence.
Why secondary dominants enrich harmony
The central idea is that any diatonic major or minor chord can be temporarily promoted to a tonic by giving it its own dominant, and that promotion is what a secondary dominant does. The raised leading tone is the key ingredient: it is a chromatic note borrowed from the target chord's scale, and its half-step pull is exactly what makes a dominant sound like a dominant. By inserting V/V before V, or V7/IV before IV, a composer intensifies the drive to that chord and adds chromatic color without leaving the key. This is why secondary dominants are so common in tonal music: they let the harmony reach toward many chords with the same strong dominant pull that normally only the tonic enjoys. Recognizing the borrowed accidental and asking "the dominant of what?" is the whole skill, and it leads directly into the part-writing and the secondary leading-tone chords of the rest of Unit 7.
Identifying a secondary dominant
To identify a secondary dominant, find a chromatic chord that is major or a major-minor seventh, see which diatonic chord it resolves to like a dominant (down a fifth or by the leading-tone pull), and label it V (or V7) of that chord, naming the borrowed accidental as the raised leading tone of the target.
Try this
Q1. What does the slash mean in the label V/V? [1 point]
- Cue. "Of": V/V is the dominant of the dominant, the chord that tonicizes V.
Q2. How does tonicization differ from modulation? [2 points]
- Cue. Tonicization is a brief emphasis on a chord with no cadence, so the home key stays; modulation establishes a new key, confirmed by a cadence.
Exam-style practice questions
Practice questions written in the style of College Board exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
AP 2021 (style)1 marksSection I (multiple choice, written). In C major, a D major triad (D, F sharp, A) appears and resolves to G major (V). How is the D major chord labelled? (A) II (B) V/V (C) ii (D) bIIShow worked answer →
The correct answer is (B) V/V.
A D major triad in C major is the dominant of G (the V chord), so it is a secondary dominant, V of V, written V/V. The F sharp is the borrowed leading tone of G, tonicizing the dominant before it arrives.
(A) uppercase II is not standard; the diatonic supertonic in C is ii (minor). (C) ii would be D minor (D, F, A), but this chord has F sharp, so it is not diatonic. (D) flat-II is the Neapolitan, a different chromatic chord. The trap is calling the chromatic chord ii; the F sharp makes it a major triad acting as the dominant of G, hence V/V.
AP 2023 (style)3 marksSection II (free response, harmonic analysis). In F major, a chord G, B natural, D, F appears and moves to C major (V). Identify the chord with secondary-dominant notation, name the borrowed accidental, and explain the tonicization.Show worked answer →
A 3-point analysis question.
(1 point) The chord G, B natural, D, F is a G dominant seventh (major triad plus minor seventh). It resolves to C major, which is V in F major, so the chord is V7 of V, written V7/V.
(1 point) The borrowed accidental is B natural, which is the raised leading tone of C (scale degree 7 of the tonicized key); in F major B is normally B flat, so the B natural signals the secondary function.
(1 point) The tonicization makes C (the dominant) feel momentarily like a temporary tonic, because it is approached by its own dominant seventh; the home key F major is not abandoned, since there is no cadence in C, just a brief tonicization.
Markers reward the V7/V label, identifying B natural as the borrowed leading tone of C, and explaining that the dominant is briefly tonicized without leaving the home key.
Related dot points
- Topic 7.2 Part Writing of Secondary Dominant Chords: part-write secondary dominants, resolving the raised leading tone up and the chordal seventh down into the tonicized chord.
A focused answer to AP Music Theory Topic 7.2, covering how to part-write secondary dominants, resolving the borrowed (raised) leading tone up by step and the chordal seventh down by step into the tonicized chord, spelling the chromatic accidental correctly, and avoiding parallels, with a worked resolution.
- Topic 7.3 Tonicization through Secondary Leading-Tone Chords: identify secondary leading-tone chords (vii diminished/V, vii diminished 7/ii, and so on) and the tonicization they create.
A focused answer to AP Music Theory Topic 7.3, covering secondary leading-tone chords (vii diminished and vii diminished 7 of a target), how they tonicize like secondary dominants, the difference between half-diminished and fully diminished sevenths, the slash notation, and distinguishing them from secondary dominants, with a worked identification.
- Topic 4.3 Harmonic Progression, Functional Harmony, and Cadences: explain tonic, predominant and dominant function, the normal direction of progressions, and the four cadence types.
A focused answer to AP Music Theory Topic 4.3, covering functional harmony (tonic, predominant, dominant), the normal flow tonic to predominant to dominant to tonic, and the four cadences (perfect authentic, imperfect authentic, half, plagal, with the deceptive cadence), with a worked cadence analysis.
- Topic 3.3 Seventh Chords: build a seventh chord by adding a seventh above the root, and identify its quality (major, dominant, minor, half-diminished, fully diminished).
A focused answer to AP Music Theory Topic 3.3, covering the seventh chord as a triad plus a seventh above the root, the five common qualities (major, dominant or major-minor, minor, half-diminished, fully diminished), how the triad and the seventh combine, and the diatonic sevenths of a key, with a worked build.
- Topic 1.5 Major Keys and Key Signatures: identify and notate major key signatures, order the sharps and flats, and use the circle of fifths.
A focused answer to AP Music Theory Topic 1.5, covering major key signatures, the fixed order of sharps and flats, the circle of fifths, and shortcuts for naming a key from its signature, with a worked identification.
Sources & how we know this
- AP Music Theory Course and Exam Description — College Board (2024)