Secondary Leading-Tone Chords
Same job as a secondary dominant — tonicizing a chord that isn't the tonic — but built a half-step below the target instead of a 5th, for a softer, more chromatic pull.
What is a secondary leading-tone chord?
In the home key, the vii° chord is built on the leading tone — a half-step below the tonic — and resolves upward into I. A secondary leading-tone chord applies that exact same relationship to any other diatonic chord: build a diminished triad or diminished 7th chord a half-step below your target, and it resolves up into that chord just like a real leading-tone chord resolves into a tonic.
These are notated the same way as secondary dominants, with a slash: vii°7/V is the leading-tone 7th chord of V. vii°7/ii is the leading-tone 7th chord of ii. The target on the right of the slash is always the chord being tonicized.
Softer than a secondary dominant
A secondary dominant's root leaps a perfect 5th down into its target — strong, assertive motion. A secondary leading-tone chord's root only creeps a half-step up into its target. Both chords contain the same tritone and both create the same tonicizing pull, but the half-step root motion makes the leading-tone version sound smoother and more chromatic, almost like the target chord is "sliding" into place rather than being announced.
Fully diminished vs. half-diminished
Most secondary leading-tone chords in practice are fully diminished 7th chords — stacked in minor 3rds all the way up (root, minor 3rd, diminished 5th, diminished 7th) — because that symmetry makes them extremely flexible for reinterpretation and voice leading. A half-diminished version (with a minor 7th instead of a diminished 7th) is possible too, but sounds noticeably gentler and is used less often as a tonicizing chord.
Common questions
What is a secondary leading-tone chord?
A diminished triad or diminished 7th chord built a half-step below a diatonic chord other than the tonic, used to tonicize that chord — similar to a secondary dominant, but a half-step below instead of a 5th.
What does vii°7/V mean?
A fully diminished 7th chord a half-step below the V chord, functioning as V's own leading-tone chord and resolving up into V.
How is this different from a secondary dominant?
Both tonicize the same targets, but a secondary dominant's root leaps a 5th while a secondary leading-tone chord's root moves only a half-step, giving it a softer, more chromatic sound.
Are secondary leading-tone chords always fully diminished?
They can be a diminished triad, a fully diminished 7th, or a half-diminished 7th — the fully diminished 7th is the most common and colorful choice.
Hear chromatic harmony in any key
Melody Monkey's Songwriting Studio lets you drop in secondary leading-tone chords and hear them resolve instantly, in any key.
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