Using Chord Substitutions
In a sense, when employing the rules of secondary dominance, or V/V, you are substituting one chord for another. In this case, the V/V substitutes for the normal ii chord. When this is voluntary and done at will — as in jazz music — it is called a
There are many kinds of harmonic substitutions in music. One of the easiest ways to figure out some of these substitutions is to experiment with alternate bass notes. One of the common strategies is to see if a chord a third above, a third below, or a fifth below creates a pleasant alternative. These intervals can either be major or minor thirds, or perfect or diminished fifths. You want to look for notes that are common to both chords.
For instance, if you are given a C-major chord and you want to substitute something else, consider Emin, Amin7, Fmaj7, or F#min75. These four substitutions all share at least two of the same notes. But be careful. When substituting chords you often must maintain the major or minor chord tonality or the chord substitution(s) may not work. In the C-major example, the major third of Cmaj is E. In all the viable substitutions above, the E remains inviolate and untouched.
Another strategy for substitution that can be very exciting is to use any chord that fits the melody of the tune. For instance, if a G is played in the melody over the given Cmin chord, you might try an E maj7 since these both complement the melody G note. Of course, there are other options as well, too many to list here. Sometimes these kinds of substitutions can be functional or nonfunctional, depending on your taste.
One of the most famous substitutions, and one that bassists regularly use, is something called
In the blues, you may see dominant seventh chords that are not acting as V7 chord substitutions. For example, in the blues, I7 chords really are I chord functions. The same is true for IV7 chords. Needless to say, be careful with substitutions on these particular dominant sevenths.
To perform tritone substitution on any dominant seventh chord, simply find the dominant seventh chord that is a tritone (an augmented fourth or diminished fifth) away. For example, if you have a G7 chord and you wish to perform tritone substitution on it, you would play a C#7. Remember, a tritone is exactly six half steps (or frets) above or below your given root.
The reason that tritone substitution works so well is that the third and seventh tones in both the original and substituted chord are exactly the same. Looking at the G7 and C#7 chords, both share a B and an F for their major thirds and dominant sevenths. As a bassist, you can exploit this opportunity by actually performing tritone substitution at will even if the other members in the band are not necessarily performing it. Try substituting the dominant seventh chords in Figure 17-13 as you see fit. It's time to improvise!
Figure 17-13.
Tritone substitution ad lib
Possible tritone substitutions are shown in parentheses. Never attempt to use tritone sub. on major or minor seventh chords.
