Secondary Leading-Tone Chords

You’ll be able to

Build secondary leading-tone triads and seventh chords (vii°/x, vii°7/x)
Distinguish fully-diminished from half-diminished secondary function
Resolve secondary leading-tone chords to their target

The other way to tonicize

Besides a secondary dominant, a chord can be tonicized by its secondary leading-tone chord, written vii°/x. This is the diminished chord built on the leading tone of the target — the note a half step below the target’s root. Like a secondary dominant it contains the target’s leading tone and its raised tendency tones, so it pulls sharply toward x. It comes as a diminished triad (vii°/x) or, more often, a seventh chord (vii°7/x or viiø7/x).

Fully diminished vs. half diminished

Secondary leading-tone seventh chords come in two flavors. The fully diminished seventh (vii°7/x) stacks three minor thirds and works to tonicize either major or minor targets — its symmetry makes it very common. The half-diminished seventh (viiø7/x), a diminished triad plus a minor seventh, is used mainly when the target is a major chord. When in doubt for a minor target, the fully diminished form is the safe, idiomatic choice.

Resolving the leading-tone chord

Resolution follows tendency tones. The leading tone (the chord’s root) rises a half step to the target’s root, and the chordal seventh falls by step. Because a fully diminished seventh contains two tritones, resolve them carefully to avoid parallels — typically the diminished fifth contracts inward and the augmented fourth expands outward. vii°/x and vii°7/x resolve to x exactly as vii° and vii°7 resolve to I in the home key.

Building a secondary leading-tone chord

vii°/x is built on the note a half step below x’s root · vii°7/V in C = F♯–A–C–E♭

Stack the chord in thirds from the target’s leading tone. A fully diminished vii°7/x = three stacked minor thirds; a half-diminished viiø7/x has a minor seventh on top and suits major targets.

Worked example

In C major, spell vii°7/V (the fully diminished leading-tone chord of V) and resolve it.

1.Identify the target: V in C major is G. Its leading tone is F♯ (a half step below G).
2.Build a fully diminished seventh on F♯ by stacking minor thirds: F♯–A–C–E♭.
3.Check the stack: F♯ to A is a minor third, A to C is a minor third, C to E♭ is a minor third — a fully diminished seventh.
4.Resolve to V (G–B–D): the root F♯ rises to G, and the seventh E♭ falls to D; the inner tritones resolve stepwise into the G chord.

Answer: vii°7/V in C major is F♯–A–C–E♭ (three stacked minor thirds). It resolves to V (G–B–D): F♯ rises to G and E♭ falls to D.

Checkpoint

In C major, a secondary leading-tone chord tonicizing V (whose root is G) is built on which note?

Tip

A secondary dominant and a secondary leading-tone chord of the same target overlap heavily — V7/V (D–F♯–A–C) and vii°7/V (F♯–A–C–E♭) share three notes (F♯, A, C). Both tonicize V and both put F♯ as the leading tone; they differ only in their lowest third and top note.

Checkpoint

How is a fully diminished seventh chord constructed?

On the exam

When you find a fully diminished seventh in the middle of a phrase, test it as a secondary leading-tone chord: its root is a half step below the next chord’s root, and it resolves there. Because it is symmetrical, spelling (which note is the root) tells you which chord it tonicizes.

Answer the 2 checkpoints as you read.