Short Answer
Overview
A secondary dominant is a chord that functions as the dominant (V) of a scale degree other than the tonic. In functional harmony, it temporarily treats a diatonic chord as if it were the tonic, creating a brief sense of resolution before moving on. Typically, a secondary dominant is a dominant seventh (or a V7) built on the root a perfect fifth above the target chord, and it often includes an accidental that lies outside the home key signature.
For example, in the key of C major, the chord D7 (D–F#–A–C) is the V7 of G major, the dominant of the vi chord (G). When D7 resolves to G, the listener experiences a momentary pull toward G as if it were a new tonal center, before the progression returns to the original key. This technique adds color, tension, and forward momentum to harmonic progressions.
History / Origin
The concept of secondary dominants emerged during the Baroque era as composers explored richer harmonic vocabularies. French theorist Jean‑Philippe Rameau (1683–1764) described the practice in his seminal work “Traité de l’harmonie” (1722), using the term “dominante secondaire” to denote a dominant that resolves to a chord other than the tonic. The practice became a staple of the Common Practice Period (c. 1650–1900), appearing in the works of J.S. Bach, Mozart, and later in Romantic composers such as Beethoven and Brahms.
How It’s Used
Secondary dominants appear in a wide range of musical styles. In classical and romantic orchestral writing, they are employed to smooth voice leading and to heighten dramatic moments. Jazz musicians use them extensively for improvisation, often altering the chord quality (e.g., using altered dominant extensions). Pop, rock, and film music employ secondary dominants to add surprise and emotional lift, frequently notated with accidentals in the chord symbol (e.g., V7/V, V7/ii).
Why It Matters
Understanding secondary dominants equips musicians with tools to analyze and create more expressive harmonic progressions. Listeners often perceive the brief tension‑release cycle as a moment of heightened expectation, which contributes to the emotional impact of a piece. Notable examples include the opening of Beethoven’s “Pathétique” Sonata, where a V7/vi leads to a minor submediant, and the pop classic “Let It Be” by The Beatles, which uses a V7/IV to shift toward the subdominant.
Common Misconceptions
A secondary dominant is the same as a modulation.
A secondary dominant temporarily tonicizes a chord without establishing a new key, whereas modulation involves a sustained change of tonal center.
Only dominant sevenths can function as secondary dominants.
While dominant sevenths are most common, any dominant‑type chord (e.g., V, V9, V13) can serve as a secondary dominant if it resolves to its target chord.
FAQ
Can a secondary dominant resolve to any chord?
It typically resolves to the diatonic chord whose root is a perfect fifth below the secondary dominant, but composers may voice‑lead to related chords for creative effect.
How is a secondary dominant notated in lead sheets?
Most lead sheets use the format V7/X, where X indicates the target chord (e.g., V7/IV for a dominant seventh resolving to the subdominant). Accidentals are added as needed.
Do secondary dominants appear in minor keys?
Yes. In minor keys, the secondary dominant often includes a raised third (e.g., V7/V in A minor is E7, which contains G♯, an accidental outside the natural minor scale).
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