Chord Substitution - Part 1 - Scalar Substitution
Let’s shift gears this month and look at a different topic, chord substitution. You can enhance a chord progression, or for that matter, your improvisation by using chord substitution. This is also a method to reharmonize a piece of music for solo arrangements to make them more interesting. In addition, this can add either tension or motion to your chord progressions and solos.
We will start in Part 1 with basic substitutions with the chords that are contained in the Major scale, and then move on to other types in future articles. To review, the I and IV chords are major sevenths, the II, III, and VI chords are minor sevenths, the V chord is a dominant seventh, and the VII chord is a half diminished (m7-5) chord. The first type of substitution that we will consider is for a I chord.
Take a Cmaj7 chord for example. The first substitute for this I chord in the key of C is the III chord. Cmaj7 consists of the notes C, E, G, and B. The III chord is Em7, which consists of E, G, B and D. Notice that the Em7 has the common notes E, G, and B. The D in this case would function as the 9, giving us a rootless Cmaj9 chord. In a chord progression this would change your bass line, and from an improvisational point of view, this would let you extend the chord in your solo.
Looking at an example, take your basic I, VI, II, V progression. You start with Cmaj7, Am7, Dm7, G7 and then, using the III substitution for the I, you end up with Em7, Am7, Dm7, G7, which gives you a different bass line for the progression, and changes the quality of the first chord.
Next, you can substitute the Vi chord for the I chord. You are starting with, Cma7, which consists of C, E, G, and B, and substituting Am7, which contains the notes A, C, E, and G. In Am7, you have the common notes C, E, G, and then the A, which is the 6. Notice that Am7 has exactly the same notes as C6. The rule to remember is that the relative minor seventh chord contains the same notes as the major sixth chord that it is relative to. For example Em7 and G6 contain the same notes.
Moving on to the IV chord, which in the key of C is Fmaj7, you can substitute the II chord, which is Dm7. Fmaj7 is built using the notes F, A, C, and E. In the case of Dm7, we have D, F, A, and C. The notes F, A, and C are common to both chords and the D functions as the 6. Sound familiar? That is the Major to Relative Minor relationship that we just discussed. So we have this come up twice within the Major scale.
The last example is the V chord. The G7 chord is constructed with the notes G, B, D, and F. For this, substitute the VII chord, Bm7-5 which is B, D, F, and A. The common notes here are B, D, and F. The A note functions as a 9, giving us a rootless G9 chord, which like with the I chord, changes the bass line, or extends the chord to the ear of the listener in a solo line.
Any of these can be used separately or in combination according to your taste. This is a simple beginning to making your chord progressions and solo line more interesting and colorful. As always, let your ear be your guide as to whether the choices sound good or not. There is no right or wrong here other than how it sounds. As with anything, learning how much to do this takes a lot of trial and error, but in time, it can really help your ideas and progressions sound fresher and much more interesting to the listener.