Here’s a fairly simple way to add a rather modern sounding chord substitution over the iii-VI-ii-V-I “turnback” progression so often found in standard songs. Take a look at the example above.
In the first two measures, I’m using four different minor triads ascending in minor 3rds. Each of these triads is converted into a four-note melodic cell by adding the major 3rd of the minor triad as the fourth note to function as a passing tone. So in the example above we have E minor (with a G sharp as the connecting passing tone), to G minor (with the B natural as the connecting passing tone), to Bb minor (with the D natural as the connecting passing tone), to Db minor (with the F natural as the connecting passing tone). So to be clear, if you were to just look at the first three eighth notes of each chord in the first two measures, you’ll see E minor, to G minor, to Bb minor, to Db minor.
This ascending minor chord movement hints slightly at the “Coltrane Matrix” in its sound and symmetrical organization. And because of “non-chordal” passing tone added to complete the four-note cell, the line has a sinewy, winding quality that creates a dissonant, yet harmonically related line over the chord changes. If you analyze the notes from a harmonic point of view, you’ll see several altered tensions. For example, the Db and Ab in measure two (as the flatted 5th and flatted 9th over the G7 chord).
The line continues over the C maj7 chord with two secondary triads (E minor and A minor) that are organized into four-note cells (again, by adding a chromatic passing tone). It finishes by breaking slightly from the four-note cell pattern with a purely diatonic shape that ends on the major 7th.
If you’d like to explore more deeply into the vast possibilities of four-note triad cells, please consider my e-book, Four-Note Diatonic Triad Cells: Comprehensive Studies in Leading Tones. And, if you’d like to more specifically explore symmetrical harmonic relationships , please consider these e-books: The Coltrane Matrix: 40 Unique Melodic Ideas in All 12 Keys, Diminshed Scale Diatonic Triad Pairs, and Augmented Scale Diatonic Triad Pairs. Click the link below to download a free pdf of this etude: