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Seventh Chords

Triads are the basic building blocks in tertian harmony. We saw in the last chapter that you use the 1st, 3rd, and 5th degrees of a scale to build a triad. To build a seventh chord, simply add the 7th scale degree on top of this triad. You end up with the 1st, 3rd, 5th, and 7th scale degrees in your chord.

You can use any of the four types of triads to make a seventh chord.

Inversions​

All seventh chords can be played as inversions, just as triads can. But in this case there is one more inversion, since there is one more note in the chord. The inversions are as follows: if the root is in the bass, the chord is in root position; if the 3rd is in the bass, the chord is in first inversion; if the 5th is in the bass, it's in second inversion; and if the 7th is in the bass, it's in third inversion.

Third inversion seventh chords sound like they want to resolve, or move to the next chord, in very specific ways. Listen carefully when you attempt to use them and be sure you're not creating tension without clearly resolving it. Usually the bass note (which is the 7th of the chord in this inversion) wants to move down one half or one whole step. If the next chord allows this, great. If not, it may sound unresolved.

Major Seventh Chords​

Building From Scales​

Since major sevenths are major sounding chords we'll use a major scale to find their component notes. Use the 1st, 3rd, and 5th scale degrees for the 1, 3, and 5 of the chord, skip the 6th scale degree, and use the 7th degree to make the 7th of the chord.

C major seventh chord is made up of the notes C, E, G, and B - for the 1, 3, 5, and 7 of the chord, respectively - all taken straight and unaltered from the C major scale.

The Intervallic View​

A major seventh chord is made up of a major triad (a major 3rd on the bottom and a minor 3rd on top) with a major 3rd on top of it. The larger, outer interval formed by this stack of three 3rds is a major 7th.

Usage​

Major seventh chords are not used a great deal in the blues except for jazz-style blues, where they are often used for the I and IV chords. They are also used in a fair amount of more modern rock and especially in R&B tunes. You'll recognize their sound.

If you play against a major seventh chord using a scale which has a flat 7th in it, which most blues scales do, it will clash very strongly with the natural 7th in the chord. In playing against a major seventh chord, you're restricted to using either a major scale, a mode or scale with the natural 7th in it, or a scale that has no 7th in it at all, like the major pentatonic scale described in detail in Blues You Can Use.

Dominant Seventh Chords​

Building From Scales​

Dominant seventh chords can be built very easily by taking a major seventh chord and flatting the 7th. Though sometimes called major-minor seventh chords because they are a major triad with a minor seventh as the outside interval, we'll refer to them as dominant sevenths throughout this book.

C dominant seventh chord is made up of the notes C, E, G, and Bb for the 1, 3, 5, and b7 of the chord, respectively.

The Intervallic View​

This chord stacks up as a major triad (a major 3rd on the bottom and a minor 3rd on the top) with a minor 3rd on top. As indicated above, the outer interval is a minor 7th.

Usage​

Dominant seventh chords are used extensively in the blues as well as in rock, R&B, and jazz. In a blues progression, they can be used for the I, IV, and V chords. They give a little more "bite" than plain major and minor chords.

Minor Seventh Chords​

Building From Scales​

Minor seventh chords are built the same way as major sevenths are, just using the natural minor scale instead of the major scale. Notice that the 3rd and 7th degrees of the scale are flatted, giving you a 1, b3, 5, and b7 for the notes of the chord.

The notes of the C minor seventh chord are C, Eb, G, and Bb for the 1, b3, 5, and b7 of the chord, respectively.

The Intervallic View​

The minor seventh chord is a minor triad (a minor 3rd on the bottom and a major 3rd on top) with a minor 3rd on top.

Usage​

Minor seventh chords can be used for the i, iv, and v chords in minor blues progressions, and for other chords in major keys, as we'll see later in this book. They're used extensively in rock, R&B, and jazz, as well as in the blues.

You'll notice the only difference between minor seventh and dominant seventh chords is the 3rd, just as it is with triads. Again you can see that the 3rd of the chord is an extremely important note. In fact, if you were to omit the root and 5th of the chord, it would still be heard as a seventh chord in the context of the chord progression especially if the bass provided the root.

Diminished Seventh Chords​

Building From Scales​

The notes of the C diminished seventh chord are C, Eb, Gb, and Bbb for the 1, b3, b5, and bb7 (double-flatted seventh) of the chord, respectively.

Since there are twelve notes (twelve half steps) to an octave, and minor 3rds are made up of three half steps, the octave is divided up evenly by the four notes of the chord (4 x 3 frets = 12 frets)

The Intervallic View​

Diminished seventh chords are made up of a diminished triad with a minor 3rd on top which creates a double-flatted seventh (bb7th).

Thanks to its unique symmetrical interval structure, the same fingering shape can be used for each inversion of the diminished seventh chord, simply by moving the shape up the fingerboard three frets at a time.

Due to the unique way they are symmetrically constructed, any one of the four notes in the chord can be the root. A diminished seventh chord made up of the notes C, Eb, Gb, and Bbb can be a C dim7, Eb dim7, Gb dim7, or Bbb dim7 (which we'll call A dim7). The reason we use a Bbb note (and not an A) in the chord is we have to build our chords with 3rds, so we need to use every other letter name to spell them. You could, for example, "re-spell" Gb dim7 to make it an F# dim7 (using the enharmonic notes F#, A, C, and Eb). Just remember to use every other letter name and flat or sharp them, if necessary, to make intervals of minor 3rds.

Usage​

There are not a lot of places where you find a use for diminished seventh chords in blues-based music. One of the most common uses is as a passing chord, when moving from a IV to a I chord.

Another is as a substitute for a V chord, using the diminished chord based on the natural 7th degree of the scale.

Chords​

By Type​

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By Inversion​


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