What is a Secondary Dominant?

A secondary dominant is a chord that temporarily acts as the dominant (V) of a chord other than the main tonic within a key. It creates a brief moment of tension that resolves to a chord that is not the primary tonic of the piece. This technique helps emphasize a particular chord and adds variety to chord progressions.

For example, in the key of C major, the dominant chord is G major, which normally resolves to C major. However, if a composer wants to emphasize the D minor chord (the ii chord), they might use an A major or A7 chord before it. In this case, A7 functions as the dominant of D minor, even though D minor is not the tonic of the key.

Secondary dominants are commonly written using Roman numeral notation such as V/V or V/ii, which means “the dominant of another chord.” They are widely used in classical, jazz, pop, and many other musical styles. By briefly introducing the dominant of another chord, secondary dominants help create stronger harmonic movement and richer chord progressions.