Seventh chords add a lot of flexibility to your songwriting toolbox. It’s amazing how the addition of one extra note multiplies the number of options available. However, a seventh chord is fundamentally still very similar to the basic chords you’ve already learned about. In the next chapter, we’ll introduce you to your first chords that use notes outside the major scale. Before we continue, here is a summary of the key points in this chapter, along with some questions to check your understanding:

Progression	Bassline
vi → vi⁴₂ (vi⁷ in third inversion) → IV	6 5 4
I → I⁴₂ (I⁷ in third inversion) → vi	1 7 6
ii → I⁶ (I in first inversion) → ii⁶₅ (ii⁷ in first inversion) → V	2 3 4 5

Check for Understanding

Explain the difference between the following chords:

I⁷ in the key of G Major
V⁷ in the key of C Major
ii⁷ in the key of F Major

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All three of these chords are seventh chords with a G in the bass, however each chord has a different quality:

Gmaj7 (major seventh)
G7 (dominant seventh)
Gm7 (minor seventh)

Check for Understanding

How many seventh chords contain (at least) the scale degrees 3, 5, and 7? What are they?

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There are two seventh chords that use scale degrees 3, 5, and 7:

iii⁷ (3, 5, 7, 2)
I⁷ (1, 3, 5, 7)

Check for Understanding

In Hooktheory I , we learned that a scale degree is said to be strongstable over a chord if the chord contains that scale degree. Consider the following melody below. What seventh chords could be used to accompany this melody so that it is stable?

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In order for the melody to be stable, the accompanying chord must have both scale degrees 1 and 6. There are three seventh chords that contain scale degrees 1 and 6:

ii⁷ (2, 4, 6, 1)
IV⁷ (4, 6, 1, 3)
vi⁷ (6, 1, 3, 5)

Check for Understanding

When jazz keyboardists play chords in a combo (an ensemble with a drummer and bassist), they often leave out the bottom note of a chord. This is largely to avoid redundancy with the bass player who will likely be playing this note. For example, if a song calls for a Cmaj7, (C, E, G, B), the keyboardist will play only the E, G, and B, and let the bass player cover the bottom C.

Let’s say you are the keyboardist in a jazz ensemble that follows this rule. If a song requires you to play a chord with major seventh quality, what is the quality of the chord that you will actually end up playing? Hint: write out the scale degrees for a major seventh chord you know, then remove the bottom scale degree. What is the quality of the resulting chord?

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Minor

There are two major seventh chords (I⁷ and IV⁷), but the answer is the same in either case. Say the music calls for a I⁷ chord, which has scale degrees 1, 3, 5, and 7. Since the bass player is playing the 1, we will play 3, 5, and 7: a iii chord with minor quality. Repeating this for a IV⁷ chord with scale degrees 4, 6, 1, and 3, we see that we would play 6, 1, and 3, a ivi chord that also has a minor quality.

The reason this works is that the spacing between the notes in a chord is precisely what defines a quality in the first place. Major seventh chords always have note gaps of (4, 3, 4). By removing the bass note, the resulting gaps would be (3, 4) which is the definition of minor quality.

Let’s say instead that you are playing a chord with a minor seventh quality. What is the quality of the chord that you will actually end up playing after dropping the bass?

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Major

There are three minor seventh chords (ii⁷, iii⁷ and vi⁷), but as before the answer is the same in either case. Take for instance ii⁷, which has scale degrees 2, 4, 6, and 1. Since the bass player is playing the 2, we will play 4, 6, and 1: a IV chord with major quality.

Check for Understanding

How many chords of different quality can you name that have scale degree 6 in the bass (inverted chords count)? Hint: there are five total.

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Major, major seventh, minor, minor seventh, half-diminished seventh

Check for Understanding

While reading chord progressions online, you run across a song that has a C7 and a gm7 in it. From what you know about chord quality, what key is this song probably in?

C Major
G Major
F Major
Eb Major

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c. F Major

We are looking for a key where seventh chords built on C have a dominant seventh quality (C7) and seventh chords built on G have a minor seventh quality (gm7). In the key of F, the seventh chord built on C would be a V⁷, which has a dominant seventh quality, and the chord built on G would be ii⁷, which has a minor seventh quality.

In each of the other keys, one (or more) of the chords has the wrong quality. In the key of C, we would expect the chord built on G to have a dominant seventh quality (V⁷); in the key of G, we would expect the chord built on G to have a major seventh quality (I⁷); and in the key of Eb, we would expect the chord built on C to have a minor seventh quality (vi⁷).

1.5 Summary