A secondary dominant chord is an altered chord (has at least one accidental) that has a dominant relationship to another chord that is not the tonic of the piece of music. Composers started to use secondary dominant chords in the Baroque period and they became increasingly popular in the Classical and Romantic periods. They are still a popular tool for modern day composers.
Secondary Dominant Chords Explained
Let’s have a look at an example to help us understand these chords.
If a piece of music is in C major then the dominant chord (chord V) is G (when this chord is played it feels as though the music wants to return to the tonic – C). This dominant function relationship is one of the crucial building blocks of our sense of music being in a specific key.
For example, here is a progression in C major.
The progression moves I-II-V-I and is effective. You can hear how the music “wants” to return to the tonic (Chord I) after the dominant chord (G – chord V):
This is a typical dominant chord relationship – the V-I chord progression in this extract forms a perfect cadence.
However, if we add an F sharp to the D minor chord (chord ii) in the progression then we create a major chord (D). The new chord (D) now acts as a dominant (chord V) to the G chord that follows it:
D is the dominant chord of G and so we have created a secondary dominant relationship in the progression.
Altered chords that are major chords can often act as a chord V (dominant) in a V-I progression.
Secondary dominants are not limited to major keys.
We can perform a similar change in C minor by turning the second chord into a major chord (although we have to add 2 accidentals in order to do so in the minor key):
Examples of Secondary Dominant Chords
Altered chords acting as secondary dominants on the supertonic (second note of the scale) are very common. However, they can be created on other degrees of the scale as well.
Here are 3 examples of secondary dominants created on the 1st (tonic), 3rd (mediant) and 6th (submediant) of the scale:
When you listen to these examples you can hear that the addition of secondary dominant chords change the sound, but do not always lead to a clear modulation (key change).
For example, in the the first extract we looked at in this lesson (II-V-I) where chord II is a major chord (secondary dominant to chord V), the feel is very much that the tonic key is reinforced by this progression.
Bach uses this particular progression in his chorales to give a very definite sense of an ending.
Examples in Pieces and Songs
Secondary dominants can be a very effective means of modulating.
Have a look/listen to this very famous opening to Handel’s “Zadok The Priest”.
You can hear how the secondary dominant chords build the tension beautifully and how a secondary dominant chord built on the supertonic at the end of bar 7 leads to a definite modulation from D major to A major:
A famous contemporary example of the use of secondary dominant chords is the song “Yesterday” by The Beatles. The secondary dominant is built on the mediant on the words “troubles seemed so”.