In this new, 5 part series we’ll be looking at the importance of the dominant 7th chord and some of the more unusual places that you can use them. First off, we’ll be looking at the nature of the dominant 7th and how it affects voice leading and harmonic movement:
This is a new series where we’ll be looking at the importance of dominant 7th’s and how we can use them to make our song writing and our general approach to harmony stronger. In part 1, we will be looking at chord V in the major scale and the reason for its overwhelming presence in so much of Western music.
There are four different types of cadence; perfect, plagal, imperfect and interrupted. A cadence is a set of chords (usually 2 or 3) that either help bring about the end of a song/piece or help bring it into a new section.
Perfect cadence: V – I e.g. G7 – C
Plagal cadence: IV – I e.g. F – C
Imperfect cadence: I – V e.g. C – G
Interrupted cadence: V – VI e.g. G – Am
Try these examples to hear each cadence in a slightly wider context:
Perfect: C, Am, Dm, G7, C
Plagal: C, G, Am, F, C
Imperfect: C, Am, F, C, G
Interrupted: C, F, G, Am
As you play through these cadences, you’ll hear that the perfect cadence has the strongest sense of resolution. The imperfect and interrupted cadence gives the feeling that we are coming into new material rather than finishing what has already been established. The plagal cadence does give a sense of finality but not as strongly as the perfect cadence. Let’s have a look at why this is.
One reason for the relationship between chord V and I is the harmonic series. I’m not going to into this in this post as it’s fairly complex, but it’s worth googling and looking it up – Leonard Bernstein’s Harvard lectures (on Youtube) explain this well. I may do a standalone post on the harmonic series sometime in the future.
Other strong reasons for the V – I connection is do with dissonance and resolution, as well as some voice leading. A dominant seventh chord has the interval of a tritone/#4/b5 (all the same thing to the ear) and this interval is considered the most dissonant of all the intervals; so much so that it was banned in the church during the Renaissance period, dubbed as ‘the devil’s interval’! Let’s take a look at this:
The notes of a G7: G B D F – It’s the interval between the third and the seventh that create the tritone.
Try out this dominant seventh shape on the guitar (apologies if you’re not a guitarist!)
G7 the tritone interval
G ——10—————10—(F, the seventh)
D ——-9—————-9—-(B, the third)
If you play the tritone interval then you will hear how dissonant it sounds. Now, the art of voice leading/counterpoint is best practiced when different parts move by step. If we play a perfect cadence then we can see how chord I resolves this tritone by step. The seventh of G7 falls a semitone to E (the third of C major) and the third of G7 rises by a semitone to a C (the tonic of a C major):
G7 C tritone resolved
This is the reason that when a dominant seventh chord is played we instinctively expect to hear a major chord a fifth below, completing a perfect cadence. The dissonance created through the tritone in a dominant seventh creates an instability that leaves us wanting the resolution and stability found in chord I.
Why use this technique?
Okay, I get that it may have felt like a fairly dry post and not very practical, but it’s a foundational lesson that will set us up for the rest of the series. When there’s something in music as fundamentally important to so many genres as the perfect cadence, it’s important that we understand why. Try working out a few songs this week and see how many of them use a perfect cadence; it’s not even worth me naming some examples because there are so many!
Now that we understand the strong pull of the dominant 7th, we can take advantage of it and use it in contexts other than chord V of the major scale. In the next four parts we’ll be going further into this, so stay tuned!