Adding a seventh to a V chord creates extra tension that increases our expectation that V will resolve to I. The resulting chord is called V7, or a dominant seventh chord. We can also use V7 to resolve to vi in what is called a “deceptive cadence.” Blues, jazz and rock also frequently use dominant seventh chords for degrees of the scale besides V.
A seventh chord is essentially a triad with an extra seventh above the bass. To create one, we’ll begin with a triad and add an interval of a seventh above the root. In the example below, G is the root, and F is the seventh, stacked above the root (G), the third (B) and the fifth (D).
As we discussed, a triad can be spelled as a stack of three consecutive lines or three consecutive spaces. When we make a seventh chord, we simply add a line or space to that stack.
Here’s another way to think about it. When we make a triad in a particular key, we begin with the root and use every other note. For example, let’s use an A chord in the key of D major.
D E F# G A B C# D E
Our A chord consists of A, C# and E. We can continue that process to make a seventh chord based on A.
D E F# G A B C# D E F# G
If we add a seventh to our A chord, we have A, C#, E and G.
There are many types of seventh chords, but the one we’re currently interested in is called the dominant seventh chord, which consists of a major triad plus a minor seventh above the root. (In the example above, G is a minor seventh above A.) In pop music, the dominant seventh is simply indicated with a 7, so if you see, for example, C7, you should assume it’s a dominant seventh chord.
The dominant seventh chord is also sometimes called a major minor seventh chord, which is arguably a more accurate name when the chord appears in certain contexts. (The word “dominant” refers to the fifth degree of the scale, and the dominant seventh chord frequently has the fifth degree as its root, but it doesn’t always, particularly in the blues.) The “dominant seventh chord” label is much more common, however, so that is what we will use here, even though we’ll have to do so rather loosely.
Here are our dominant seventh chords. (Keep in mind, again, that sharps and flats cancel after each measure.)
In classical music, since the word “dominant” means the fifth degree of the scale, the root of the dominant seventh will be that fifth scale degree. Using Roman numerals, the dominant seventh will appear as V7.
So, for example, if we’re in the key of F, our fifth scale degree will be C. So our dominant seventh chord, or V7, will be C7 (C, E, G, Bb).
In the key of A, our fifth scale degree will be E, so our V7 will be E7, or E, G#, B, D.
|Quick Quiz 4.1
What will our dominant seventh chords be in the following keys? Which notes will they contain?
In classical music, the V chord creates tension, and the I chord typically resolves that tension. That tension-resolution relationship isn’t quite as crucial with V and I in pop music, but when we change V to V7, we’ll often feel very strongly that we want the chord to resolve to I.
For example, listen to the Contours’ “Do You Love Me,” which is in F major. (Ignore the Bb minor chord below and trust me on that. Or, better yet, come back to this example after you’ve read the chapter on borrowed chords and see if you can figure out what the Bb minor chord is.)
When the Contours land on “dance,” they hold it out for several measures, using the V7 chord (C7) to heighten our anticipation of what’s to come. They then resolve to F at the beginning of the “work, work” section that follows.
One reason the V7 chord sounds tense is that the third and seventh of the chord (E and Bb, if C7 is our V7 chord) form a tritone. The tritone is a dissonant interval, and our ears want that dissonance to resolve by step to the root and third of the I chord.
Often, then, the V7 chord will resolve to I. Sometimes, though, we can also have the V7 resolve to vi. In classical music, when V or V7 resolves to vi at the end of a phrase, we call it a deceptive cadence. It is “deceptive” because our ears expect V or V7 to resolve to I, and so when V or V7 resolves to vi instead, it is as if we have been tricked. The trickery is especially clever because vi has two notes in common with I. In F major, for example, vi is d minor (D, F, A), and I is F major (F, A, C).
The Dominant Seventh Chord In The Blues
In the blues and in some types of music derived from the blues (such as some rock & roll), the major minor seventh chord (which, again, is a different name for the dominant seventh chord that’s slightly more accurate in contexts like this one) need not be connected to the fifth degree of the scale, and need not be a part of the tension-resolution relationship we’ve discussed. Many blues progressions are built entirely, or almost entirely, from major minor seventh chords. For example, here’s a standard 12-bar blues progression in the key of C.
Here, the C7 is built around the I chord, while F7 is built around IV and G7 around V. The major minor chords here do not function as they do in classical music. Instead, you might think of the sevenths of these chords as ways of adding a little extra dissonance to triads. Certain elements of the blues seem faintly connected to the tension-resolution role of harmony in classical music – a V7 chord ends the 12-bar blues progression above, for example, and circles back to I as the progression begins again. But the major minor seventh chords that appear so frequently in the blues (and in jazz) are often best seen not as sources of tension to be resolved, but instead as ways of generating harmonic ambiguity for vocalists and instrumentalists to work with.
Chuck Berry’s “Johnny B. Goode” features a variation on this basic progression, also in the key of C.
We can see, then, why the major minor seventh chord is usually just labeled “7” in pop music, since pop and rock music in the American tradition derives in large part from blues and jazz. Most current pop and rock no longer uses major minor seventh chords as liberally as the blues does, however, so when the major minor seventh chord appears, it is very frequently connected to the fifth scale degree.
|Quick Quiz 4.2
Name the notes of the major minor seventh chords associated with I, IV and V in the key of Eb.
Next Chapter: Other Seventh Chords And Extended Chords
Quick Quiz Answers
What this exercise is asking is for you to find the fifth scale degree of the keys listed and build a major minor seventh chord around each of them.
Key of C major: G7 (G, B, D, F)
Eb major: Bb7 (Bb, D, F, Ab)
B major: F#7 (F#, A#, C#, E). Remember, F#, not F natural, is the fifth scale degree in B major.
I: Eb7 (Eb, G, Bb, Db)
IV: Ab7 (Ab, C, Eb, Gb)
V: Bb7 (Bb, D, F, Ab)