A secondary dominant in music is a dominant seventh chord that functions as a temporary dominant for a chord other than the tonic of the prevailing key. It creates a brief sense of tension and pulls strongly towards its target chord, which is then temporarily tonicized.
Understanding Secondary Dominants
A secondary dominant chord is essentially a dominant seventh chord built on a root that is a perfect fifth above the chord it intends to resolve to. While a regular dominant chord (V7) resolves to the tonic (I) of the key, a secondary dominant resolves to a different diatonic chord within the key, making that chord feel like a temporary tonic.
For example, in the key of C major, G7 is the primary dominant (V7) resolving to C major (I). A secondary dominant, however, might be D7, which resolves to G major (V). In this case, D7 is acting as the V7 of G. This is often notated as V7/V (read as "five-seven of five").
The core characteristic of a secondary dominant is its strong pull: it functions as the dominant of some harmonic element other than the key's tonic and resolves to that element. This resolution typically occurs downward by a perfect fifth (or upward by a perfect fourth). In jazz harmony, for instance, a secondary dominant might frequently appear on a weak beat, adding a characteristic rhythmic and harmonic drive before resolving to its target chord.
Function and Purpose
Secondary dominants serve several key purposes in musical composition and improvisation:
- Adding Harmonic Color: They introduce chromaticism and temporary dissonance, enriching the harmonic landscape.
- Creating Tension and Release: The dominant seventh quality of the chord creates a strong leading tone and a sense of anticipation that resolves pleasingly to the target chord.
- Temporary Tonicization: They temporarily emphasize a chord other than the tonic, making it feel like a brief point of arrival or stability.
- Preparing for Modulation: While not a full modulation, secondary dominants can gently steer the listener's ear towards a new key area by strongly emphasizing a chord that might become a new tonic.
- Enhancing Chord Progressions: They can add complexity and forward motion to otherwise simple chord progressions, making them more engaging.
Types of Secondary Dominants
Secondary dominants are named by referring to the diatonic chord they resolve to. In a major key, the most common secondary dominants are those that resolve to the diatonic major or minor chords (II, III, IV, V, VI). The primary tonic (I) does not typically have a secondary dominant since the V7 chord already serves that purpose.
Common Secondary Dominants in C Major
| Notation | Target Chord | Secondary Dominant | Notes |
|---|---|---|---|
| V7/II | D minor (ii) | A7 | Dominant of D minor (A7 to Dm) |
| V7/III | E minor (iii) | B7 | Dominant of E minor (B7 to Em) |
| V7/IV | F major (IV) | C7 | Dominant of F major (C7 to F) |
| V7/V | G major (V) | D7 | Dominant of G major (D7 to G) |
| V7/VI | A minor (vi) | E7 | Dominant of A minor (E7 to Am) |
Note: The target chord can be a major or minor triad depending on the key, but the secondary dominant itself is almost always a dominant seventh chord.
How Secondary Dominants Sound
When a secondary dominant is played, it creates a distinct "pull" or "leading" sensation towards its target chord. This is due to the inherent tension of the dominant seventh chord, particularly the tritone interval (e.g., C# and G in a G7 chord in C major) and the leading tone resolving to the tonic of the temporary key. The resolution provides a satisfying sense of arrival, even if only for a moment, before the music continues its journey in the original key.
Practical Applications
- Composition: Composers use secondary dominants to create variety, deepen emotional expression, and drive harmonic progression. They are found in diverse genres, from classical to jazz, pop, and film scores.
- Improvisation: In jazz and other improvisational styles, musicians frequently outline secondary dominant arpeggios or scales (like the mixolydian mode) over these chords to highlight their temporary tonicization and create sophisticated melodic lines that reflect the underlying harmony.
