Harmonic functions of dominant chords and subdominant chords
When looking at how we construct chord progressions, looking at how the tonic chord (or root) relates to other chords is important. Take dominant chords and subdominant chords in any given key. Diatonically, these chords are one fifth below (subdominant) and one fifth above (dominant) from the tonic.
Whether a fifth below or above, these two chords create a harmonic tension that provides a strong resolution to the tonic. The dominant chord is always the V chord in your diatonic chord scale, whereas the subdominant is always the IV.
For more on diatonic chords, don’t forget to read this article!
How does it sound?
In the below example, try playing the following chord progression to see how each chord sounds in relation to the next…
Here, we have a D7 chord as our dominant (V) and a C chord as our subdominant (IV). First we want to listen out for the movement between the V chord and the I chord (G in this case), and subsequently the movement from the IV to the V.
But how do dominant chords work?
Okay, in any given major key, the dominant chord is built on the fifth degree of the scale. It will usually be a major triad, but can be extended to a dominant 7, dominant 9 chord and so on. Basically, as you add more degrees of the scale you will get bigger chords.
However in a minor scale, although still the fifth degree of the scale, it is going to be a minor triad or minor 7th chord.
As you would have heard when playing the previous progression, the dominant chord has a tendency to resolve nicely to the I chord, or tonic. It allows the songwriter to create a little bit of tension whilst driving the progression to a natural conclusion. Lets take a look at another example…
A very common progression is the ii – V – I progression. The V chord being our dominant or 7th chord. Even though we’ve extended the V chord from a B7 to a B9, it still acts as the dominant chord.
So what happens if we put this in a minor key context?
Here, our B7(b9) is acting as the dominant chord, with our F# diminished acting as a m7b5 chord. A dominant 7 chord, in this case, can be substituted for alternatives that use a b9 or b13. With this progression, the resolution to the Em7 is made all the more profound due to the tension preceding it.
In both major and minor, explore different chord voicings and transpose to different keys to experiment with different sounds.
Where does the subdominant chord come in?
Subdominant chords are always set on the 4th degree of the scale, i.e the IV chord. Essentially, they create a feeling of anticipation as we move toward the dominant chord and subsequently resolve to the tonic.
In many ways, a subdominant chord conveys more of a sense of stability compared to the dominant chord. Let’s look at an example.
Here in the key of G, we’re using a ii – IV – V – I progression. The addition of the subdominant, gives the progression more of a sense of movement and stability as it gravitates toward the resolution to the tonic.
Where can I hear these progressions?
This way of writing chords is not uncommon at all. Songs such as Radiohead’s early hit, ‘Creep‘ features a subdominant movement in its first progression.
‘Creep‘ takes it one step further and switches the subdominant (C) for the minor subdominant (Cm) before transitioning back to the tonic, leaving out the dominant chord altogether. This gives us a Plagal Cadence instead of the V – I Perfect Cadence associated with the dominant chord.
To summarise….
Understanding the role of subdominant and dominant chords is a great tool to have in your locker when it comes to forming new and interesting chord progressions. The difference between a plagal and perfect cadence is subtle, but can have interesting effects to your chord progressions!
Just remember, your dominant chord is built on the fifth degree of the scale, and leans strongly toward resolving to the tonic (perfect cadence). Whilst your subdominant is built on the fourth degree of the scale, providing a more stable and contrasting sound (plagal cadence).
Subdominant chords can also act as dominants for other chords in a progression, sometimes acting as secondary dominants. They can help you shift keys as well as add harmonic intrigue to a progression.
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