Music tends to use triads in the majority of music we hear, but there are plenty of chords that go beyond just three pitches. These more complicated harmonies are typical in Jazz and Blues, and are also used with varying frequency in classical music from the Baroque period onward. This lesson will focus on one of the most common four-note chords: the dominant seventh.
"Dominant seventh" is a bit of a mouth full, so the most common way we refer to this type of chord is to drop the "dominant" and simply say "seven" following the name of the chord. For example, using a C dominant seventh as an example: C7 is the common way to write it, and we would say "C seven."
Why call a four-note chord a seventh? We know that triads are based on the first, third, and fifth notes of a scale. Seventh chords make use of the first, third, and fifth notes of the scale too, but additionally use the seventh note of the scale to create a four-note chord. Seventh chords therefore derive their name from that added note, which is the note that distinguishes them from regular triads. Seventh chords then have four parts: root, third, fifth, and seventh.
Knowing that seventh chords are built of the first, third, fifth, and seventh scale degrees of a scale, let's use this to find the notes of a C seventh chord. Using the C major scale shown below, name the notes required to create a C seventh chord.
Hopefully you found the letters needed to create a C seventh chord to be C, E, G, and B. However, there is one more step to complete before we have a C dominant seventh chord, we need to lower the seventh by a half step. This gives the C dominant seventh chord a B-flat instead of a B-natural in its spelling.
We have already seen how to construct a dominant seventh chord using the major scale, but let's make sure it's clear what needs to happen. There are three steps involved:
Let's practice this method by constructing a Bb dominant seventh chord. The scale needed is Bb major. The notes needed from the Bb scale are Bb, D, F, and A. To make the chord a dominant seventh, we lower the seventh (in this case the note A) by a half step, making the Bb dominant seventh chord's spelling: Bb, D, F, Ab.
Looking at the triads and dominant chords in the previous sections, you may have noticed that like triads, seventh chords are also constructed by stacking one third on top of another. If you have been constructing your triads by placing a major third on the bottom and a minor third on top, like in this A major triad, then constructing dominant sevenths just requires one more minor third be placed above the fifth of your major triad. This means that the "recipe" for a dominant seventh chord becomes a series of three thirds: Major 3rd, Minor 3rd, Minor 3rd, in order from lowest to highest notes.
Here are a few more examples of chords built in this fashion. Try to spell each dominant seventh chord on your own before clicking the button to see the answer.
As long as you have a major triad correctly built, it should be easy to add the single note required to make it a four-note dominant seventh chord. To create dominant seventh chords, we began by constructing a major chord, then we used two methods to add the seventh to the chord:
Depending on how comfortable you are with intervals, it is also useful to think of each chord tone in relation to the root of the chord. As you may recall, one of the methods we learned when creating triads applied a similar way of thinking: a major triad is made up of a major third and a perfect fifth above the root. To add a dominant seventh to a major triad in this fashion, we simply add a minor seventh interval (m7) above the root of the chord. The example below is an E dominant seventh (E7). First an E major triad is constructed, then the interval of a minor seventh (m7) is added above the root, resulting in a spelling of E, G-sharp, B, D.