Secondary Dominants · Jazz Wiki

A secondary dominant is a Dominant Seventh Chord built on the fifth degree of a chord other than the tonic, borrowed for a bar or two to give that chord its own miniature “V7→I” pull. It’s the tool that turns any diatonic chord — ii, iii, IV, V, or vi — into a temporary tonic, which is why a static-sounding progression like Dm7–G7–Cmaj7 can suddenly feel like it’s moving through several little keys without ever actually leaving C major.

Why “borrowing” a dominant works

Functional harmony runs on the pull of V7 to I: the leading tone wants to rise a half step, and the tritone inside the chord wants to contract inward. A secondary dominant just relocates that same mechanism onto a different target. Stack a dominant seventh a perfect fifth above any diatonic chord and you get the identical gravitational pull, aimed at that chord instead of the tonic — this brief spotlighting of a non-tonic chord is called tonicization, and it’s fundamentally different from modulation because the home key is never actually abandoned or confirmed elsewhere with a cadence.

The five secondary dominants in C major

Notation reads “V7 of x” — V7/ii means “the V7 that belongs to ii.” Every one of these chords is a major triad with a minor 7th, and each introduces at least one note foreign to C major, which is exactly what makes the ear perk up and expect the resolution.

Notation	Spelling	Resolves to	What moves
V7/ii	A7 (A–C♯–E–G)	Dm7	C♯→D (leading tone)
V7/iii	B7 (B–D♯–F♯–A)	Em7	D♯→E (leading tone)
V7/IV	C7 (C–E–G–B♭)	Fmaj7	tritone E–B♭ → F
V7/V	D7 (D–F♯–A–C)	G7	F♯→G (leading tone)
V7/vi	E7 (E–G♯–B–D)	Am7	G♯→A (leading tone)

Here are two of those five resolving, each borrowed leading tone spelled out with an explicit accidental:

In practice, V7/V is the workhorse — sharpen the ii of a plain ii-V-I into a dominant and Dm7–G7–Cmaj7 becomes D7–G7–Cmaj7, where D7 treats G as a momentary tonic before G7 turns around and does its usual job. The F♯ inside that D7 is the giveaway: one borrowed leading tone, aimed at G.

What comes before the dominant: the related ii

A secondary dominant rarely travels alone. Just as G7 is usually preceded by Dm7 in the home key, V7/ii (A7) is often preceded by its own related ii chord, Em7 — giving a complete secondary ii–V inside C major: Em7–A7–Dm7. Extend that logic further back and you get backcycling, where dominants chain a fifth apart (E7–A7–D7–G7–C) to build long stretches of forward motion out of a single circle-of-fifths gesture, the same engine that drives the circle of fifths.

Where you actually hear them: turnarounds and blues

Secondary dominants are everywhere in turnarounds and blues harmony because both forms need a jolt of energy heading into the next chorus. A 12-bar blues in F leans on this in bar 4, where the plain F7 quietly becomes V7/IV, pushing hard into the B♭7 of bar 5; jazz players routinely add D7 in bar 8 (V7/ii) to set up the Gm7–C7 that brings the chorus home — moves woven throughout the 12-bar blues tradition and taken to an extreme in the all-dominant bridge of rhythm changes. “All of Me” runs C6–E7–A7–Dm7 across its first eight bars — E7 and A7 chaining down by fifths until A7 (V7/ii) lands on Dm7 — and later uses D7 (V7/V) to set up the final G7, all inside plain C major with no modulation anywhere.

Not modulation, and not the only chromatic dominant trick

A secondary dominant tonicizes; it never confirms a new key with its own cadence, which is the line separating it from real modulation. It’s also worth distinguishing from tritone substitution, where a dominant is replaced by another dominant a tritone away (B7 for G7) rather than borrowed to target a new chord — both exploit the tritone’s pull, but they solve different problems. When you’re doing Roman numeral analysis on a lead sheet and see an unexpected accidental-laden dominant seventh resolving down a fifth to something other than I, that’s your secondary dominant — one of the first chromatic chords worth learning to spot at sight.

♫ Listen

Oscar Peterson Trio — “All of Me” (A Jazz Portrait of Frank Sinatra, 1959): the E7 and A7 in the opening bars land clearly under Peterson’s crisp touch — listen for E7 refusing to stay diatonic, then handing off to A7 (V7/ii) and into Dm7.
Bill Evans Trio — “Autumn Leaves” (Portrait in Jazz, 1960): each time the form pulls toward G minor, the D7 (V7 of the relative minor) does the pulling; Evans’ sparse voicings make its tritone resolution easy to isolate.