V/V ("five of five") is a secondary dominant chord built on the dominant of the dominant; it borrows a chromatic note (the raised 4th scale degree) to briefly tonicize V, making the dominant chord feel like a temporary tonic before resolving V/V → V.
V/V, read aloud as "five of five," is the most common secondary dominant. Instead of just moving to the dominant chord, the music treats V like a temporary tonic and approaches it with its own dominant. In C major, the dominant is G, and the dominant of G is D major (D–F#–A). That F# is the chromatic giveaway. It's the raised 4th scale degree of the home key, and it acts as a leading tone pulling up to scale degree 5.
The whole trick exploits the strongest pull in tonal music, the dominant-to-tonic resolution. By putting a dominant-quality chord in front of V, composers make the arrival on V feel inevitable. This is called tonicization. It's a brief lean toward a new key, not a full modulation. The home key never actually changes. You'll often see V/V as a triad or as V7/V (in C major, D–F#–A–C), and it resolves the same way any dominant does, with the leading tone (the raised 4) stepping up and the chordal 7th stepping down.
Secondary dominants live in Unit 7 of AP Music Theory (Harmony and Voice Leading IV: Secondary Function), and V/V is the one you'll meet first and most often. It's the gateway to chromatic harmony. Everything you learned about diatonic dominant function in Units 4 and 5 gets recycled here, just aimed at a chord other than tonic. If you can resolve V7 to I correctly, you already know how to resolve V7/V to V. The exam expects you to spell secondary dominants in any key, identify them by ear and in score analysis, and use correct voice leading when you realize figured bass or harmonize a melody. V/V also sets up modulation. A tonicization of V that sticks around long enough becomes a modulation to the dominant key, which is the most common key change in the literature.
Keep studying AP® Music Theory Unit 7
Visual cheatsheet
view galleryV/ii (Unit 7)
V/ii is the same idea pointed at a different target. Once you understand that V/V is just "the dominant of V," you can build the dominant of any major or minor diatonic chord. In C major, V/ii is A major (A–C#–E) resolving to D minor. The logic never changes, only the destination.
Closely Related Keys (Unit 7)
Tonicization is modulation's little sibling. V/V briefly tips the music toward the dominant key, and the dominant key is always closely related (its key signature differs by just one accidental). When a piece modulates to V, the V/V chord is usually the pivot moment where the new key takes over.
Circle of Fifths (Unit 1)
V/V is the circle of fifths in action. The chord sits one step clockwise from V, which sits one step clockwise from I, so V/V → V → I traces a chain of descending fifths. Chains of secondary dominants extend this pattern even further (V/V/V exists in the wild).
On multiple choice, you'll see V/V in score analysis ("the chord at measure 4 is best labeled...") and in aural questions where you hear a chromatic pull toward the dominant. The raised 4th scale degree is your visual and aural clue. On the FRQs, V/V shows up in figured bass realization and harmonizing a melody, where you have to spell it correctly in the given key and resolve it with proper voice leading. That means the raised 4 (the secondary leading tone) resolves up by step to scale degree 5, and you avoid doubling it. Practice questions frequently ask how V/V contributes to tonicization in a specific key, so be ready to explain the mechanism, not just label the chord. In C major, that means naming D major (with F#) as the chord that makes G feel like a temporary tonic; in G major, it's A major (with C#) tonicizing D.
In a major key, V/V and ii share the same root. They differ by one note. In C major, ii is D minor (D–F–A) and V/V is D major (D–F#–A). That single raised third changes everything functionally. The chord stops being a predominant and becomes a dominant aimed at V, because the F# now acts as a leading tone to G. If you see scale degree 2 in the bass with a raised 4 in the chord, label it V/V, not ii.
V/V is the secondary dominant that tonicizes the dominant chord, making V briefly sound like a tonic before the music resolves V/V → V.
Spell V/V by building a major triad (or dominant 7th) on scale degree 2 of the home key, which means raising scale degree 4 with an accidental.
The raised 4th scale degree functions as a secondary leading tone and must resolve up by step to scale degree 5; don't double it.
V/V causes tonicization, not modulation, because the home key returns immediately after the resolution.
In C major, V/V is D major (D–F#–A); in G major, V/V is A major (A–C#–E). The chromatic note is always the giveaway in both score and ear-training questions.
V/V is often the pivot point when a piece actually does modulate to the dominant key, the most common modulation in tonal music.
V/V ("five of five") is a secondary dominant, a major or dominant-7th chord built on scale degree 2 that resolves to the V chord. In C major it's D major (D–F#–A) resolving to G, briefly making G sound like a tonic.
Tonicization. V/V leans toward the dominant key for just a chord or two, then the home key resumes. A modulation requires the new key to actually take over, usually confirmed by a cadence in the new key.
They share a root but differ in quality and function. In C major, ii is D minor (a predominant) while V/V is D major (a dominant aimed at V). The raised third of V/V (F# in C major) acts as a leading tone to scale degree 5, which ii doesn't have.
Treat it like any dominant resolving to its tonic. The secondary leading tone (raised scale degree 4) steps up to scale degree 5, the chordal 7th (if present) steps down, and you avoid doubling the chromatic note.
Because a dominant chord needs a leading tone a half step below its target. To tonicize V, the chord needs a half step below scale degree 5, and that note is the raised 4th scale degree (F# when tonicizing G in C major).
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