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from Jazzin' the Blues
Building Extended Dominant Chords
Let’s look at a couple of ways to build on simple 7th chord structures. First, we’ll build a 13th chord from a 1–7–3–5 voicing.
A G7 chord would, from the bottom up, consist of the notes G (1)–F (¯7)–B (3)–D (5). The 6th scale degree is one whole step (two frets) above the 5th. The 6th is the same note as the 13th—E in a G chord. If you simply move the D (5) on the second string up to an E (6 or 13), you get a G13 chord. What makes it a 13th as opposed to a 6th is the presence of the 7th of the chord below the 13th. You can flat the 3rd to get a minor 13th chord or raise the 7th to make a major 13th chord.
The other chord we’ll build is a dominant 9th. This we will build from the 5–3–7–1 structure.
Starting with a D7 chord, you move the D (1) on the second string up two frets to an E (9). Adding the 9th to a 7th chord results in the creation of a dominant 9th chord. In order to voice a complete 9th chord on the guitar we have to rearrange some other notes as well. The 5th is moved from the sixth to the first string—two octaves up. Also, we have to move the root from the second string to the fifth string—one octave down. As with the 13th chord, you can flat the 3rd or raise the 7th to create a minor 9th or major 9th chord, respectively. Look at the following figure to see the 9th chord variations graphically.
Once you’ve built a dominant 9th chord, you can alter the 9th (sharp or flat it), resulting in a 7˜9 or 7¯9 chord. All of the resulting chords are dominant. Here they are.
The Relative Minor Substitute
This lesson’s chord progression moves from the I (G13) to the VI chord (E7˜9) in bar 8. This is not an arbitrary chord change. Instead, it is chord substitution.
Usually a vi chord is a minor seventh chord. It can serve as a substitute for the I chord. In the key of G, the I7 chord (G7) contains the notes G(1)–B(3)–D(5)–F (¯7). A vi7 chord (Em7) is made up of the notes E(1)–G(¯3)– B(5)–D(¯7). You can see that they have three notes in common—G, B, and D. That makes them closely related. In fact, the vi chord is called the relative minor of the I chord. They are interchangeable and can substitute for each other. Take a look at the following figure for a graphic view of this principle. It is important to understand it because we will use it with other closely related chords.
Changing Chord Quality
Now, here’s the twist: in jazz, we often use a relative minor 7th chord as a substitute for a dominant chord (for example, substitute Em7 for a G7). Then, we change the minor 7th substitute to a dominant chord! We change it from a diatonic chord (of the key) to a chromatic chord (altered with a note or notes from outside the key). In the above example, change the Em7 to an E7, which makes for a stronger chord movement. It works like this:
|Original Chord||Substitute||Substitute Made Dominant|
|G7 (I)||Em7 (vi)||E7 or E7˜9, etc. (VI)|
One last detail: instead of jumping down three half steps from the I to the VI chord in bars 7 and 8, we “walk down” by half step, filling in the gap between G and E chords (G13–G¯13–F13–E7˜9). You can always play chords on the half steps between two chords. The essential chord progression doesn’t really change. It’s still a I–VI movement, but embellished by the passing chords (G¯13 and F13), which simply fill in the space between the essential chords of the progression (G13 and E7˜9). Passing chords don’t really change the basic chord movement. You can ignore them when improvising. By using the same chord voicings on the first three chords, the walkdown sounds smoother.
The comping rhythm alternates between the 13th (G13 and C13 chords) and 7th (G7 and C7 chords). Both are built on the 1–7–3–5 structure. You simply strum the G13 twice and then the G7 twice using one strum per beat. The same rhythm figure is used on the C7 and C13 chords.
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This solo makes use of the G blues scale almost entirely, forcing it over the progression. Because the tune is a blues, it works even though the chord changes are somewhat different from a traditional blues. It also has chord hits, or punctuations, made of chord fragments: only the top three notes of the G13 and C9 chords. They are a little cleaner-sounding in a solo than the larger, complete chords. They are also handier to grab.
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