How can a leading-tone chord, rather than a dominant, tonicize another chord?
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.
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What this topic is asking
The College Board (Topic 7.3) wants you to identify secondary leading-tone chords (vii diminished or vii diminished 7 of a target chord) and the tonicization they create, recognizing that like secondary dominants they borrow the leading tone of a chord other than the tonic.
Secondary leading-tone chords
To find one, look for a diminished triad or diminished seventh built a half step below a diatonic chord, resolving up into that chord. The chord it resolves to is tonicized.
Two seventh qualities
Choosing the quality depends on the target chord and the desired color, but the function, tonicizing the target through its leading tone, is the same.
Why a rootless dominant still tonicizes
The central idea is that what makes a dominant tonicize is not its root but its tendency tones, and the leading-tone chord keeps those tones while dropping the root. A secondary dominant V7 of a target contains the target's leading tone (pulling up) and a seventh (pulling down); the leading-tone chord vii diminished 7 of the same target contains the same leading tone and similar tendency tones, just without the dominant root (scale degree 5 of the target). Because the strongest pull comes from the half-step leading tone, the leading-tone chord tonicizes just as convincingly, with a lighter, rootless sound that is easy to slip into a texture. This is why composers use secondary leading-tone chords interchangeably with secondary dominants: they reach the same target with the same chromatic pull. Recognizing them is the same question as before, "the leading tone of what?", applied to a diminished chord.
Identifying a secondary leading-tone chord
To identify one, find a diminished triad or diminished seventh built a half step below a diatonic chord, confirm it resolves up into that chord, and label it vii diminished (or vii diminished 7) of that chord, naming the borrowed leading tone.
Try this
Q1. On which scale degree of the target chord is a secondary leading-tone chord built? [1 point]
- Cue. On the leading tone of the target (a half step below it), borrowed chromatically.
Q2. How does a secondary leading-tone chord differ from a secondary dominant while tonicizing the same target? [2 points]
- Cue. It keeps the leading tone and tendency tones but omits the dominant's root, so it tonicizes with a lighter, rootless sound.
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 fully diminished seventh chord F sharp, A, C, E flat resolves to G major (V). How is it labelled? (A) vii diminished 7 of V (B) V7 (C) ii diminished 7 (D) bVIIShow worked answer →
The correct answer is (A) vii diminished 7 of V.
The chord F sharp, A, C, E flat is a fully diminished seventh built on F sharp, the leading tone of G. Since it resolves to G (V in C major), it is the secondary leading-tone seventh of V, written vii diminished 7 of V; the F sharp pulls up to G as a borrowed leading tone.
(B) V7 would be a major-minor seventh, not a diminished seventh. (C) ii diminished 7 is diatonic in minor on scale degree 2, not this chromatic chord. (D) flat-VII is a different chord. The trap is missing that the diminished seventh on the raised leading tone of a target chord is a secondary leading-tone chord, not a diatonic chord.
AP 2023 (style)3 marksSection II (free response, harmonic analysis). In F major, a chord E, G, B flat appears and resolves to F major (I). Identify the chord, label it, and explain why it tonicizes the tonic, comparing it to a secondary dominant.Show worked answer →
A 3-point analysis question.
(1 point) E, G, B flat is a diminished triad built on E, the leading tone of F. Resolving to F (the tonic, I), it is the leading-tone chord of I, vii diminished (here a diatonic leading-tone chord since E and B flat are in F major).
(1 point) It tonicizes (here confirms) the tonic because E is the leading tone pulling up to F and B flat is the chordal tendency pulling down, framing the tonic like a dominant would.
(1 point) Compared with a secondary dominant, a leading-tone chord lacks the root of the dominant (it omits scale degree 5) but keeps the two strongest tendency tones, so it tonicizes the same target with a lighter, rootless sound.
Markers reward identifying the diminished leading-tone chord, explaining the tendency tones that frame the target, and contrasting it with a secondary dominant (no dominant root, same pull).
Related dot points
- Topic 7.4 Part Writing of Secondary Leading-Tone Chords: part-write secondary leading-tone chords, resolving the borrowed leading tone up and the diminished and seventh intervals correctly.
A focused answer to AP Music Theory Topic 7.4, covering how to part-write secondary leading-tone chords, resolving the borrowed leading tone up by step, the chordal seventh down by step, the diminished fifth inward, avoiding the doubled tendency tone, and spelling the chromatic notes, with a worked resolution.
- 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.
- 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 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 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.
Sources & how we know this
- AP Music Theory Course and Exam Description — College Board (2024)