SubProgstEx1

Substitute chord progressions offer some of the most riveting, colorful moments in jazz. But how do you justify them in theory, much less improve upon them in practice? Here is a most practical path that you can demonstrate to yourself or your students in less than an hour.

Long before encountering substitute chord progressions, most musicians come upon surprise cadences (also known as substitute cadences or sub-targets). Bach chorales are filled with countless superb examples, the simplest of which might be a V chord that instead of resolving to a I chord goes to a vi. Sometimes the chorale might quickly return to the key of the I chord; other times it might turn out that the key center has changed, with what used to be the vi now the new i chord.

To demonstrate surprise cadences, I like to play a bossa nova progression in C major that cadences on C as expected. I ask my students to sing the tonic note (root of the key) to me after the final cadence—without my singing it to them. The result looks like Example 1. (Feel free to simplify the rhythms to half-notes if needed.)

Less-experienced musicians will often sing the fifth, third, or maybe even the seventh or ninth instead of the root of the final chord. Work with them to develop the invaluable skill of hearing tonic: few bandstand tools are more useful than hearing what key you’re in at a given moment!

Once we can all agree on hearing C as tonic at the end of this progression, it’s time to demonstrate what a surprise cadence or sub-target sounds like. In Example 2 I play the same opening but end with a two-bar statement in a surprise key, here Eb major.

Hearing nine beats of Eb major is usually sufficient to prompt most in attendance to sing the Eb on their own as tonic rather than C, thus demonstrating that we have successfully modulated to another key. And the movement is quite attractive! Feel free to repeat the example for positive reinforcement.

And now the logic of the progression is self-evident: if, while in the key of C, a Dm7-G7 progression is a perfectly fine way of getting to Ebmaj7, then the same Dm7-G7 pairing should be a wonderful means of arriving at Ebmaj7 if we’re already in the key of Eb to begin with! Let’s test it in Example 3, where instead of starting in C, we start in Eb.

You can demonstrate the last several bars over and over again: it is a convincing progression.

Let’s try one in the other direction on the circle of fifths. Play a ii-V in C that lands on Emaj7, such as in Example 4.

Then cross over to the mirror-image of substitute cadence: the substitute progression. If, while in the key of C, the Dm7-G7 progression is a successful approach to Emaj7, then the same Dm7-G7 pairing should be a fine path to Emaj7 if we’re already in the key of E to start with. Let’s test it in Example 5, where instead of starting in C, we start in E.

Thus a pattern emerges, as illustrated by the chart in Example 6: the left column’s sub-target (final chord) is the inverse-equation of the lower-fraction in the right column. A minor third (left side) is inverse to a major sixth (right side), a major third to a minor sixth, and so on.

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this example.)

Sub-progressions mirror their sub-target opposites, forever related, equally viable, equally voiceable.

Such “subs” are accepted within the basic progressions of many jazz standards. For example, the ii-V/bIII-I progression lives within the eighth measure of “Stella by Starlight,” where either an Ab7 or an Ebm7-Ab7 sequence leads to a return of the tonic Bb chord in bar nine (Example 7).

If thinking of “Just Friends” in F, the same sequence (now Bbm7-Eb7) in measures three and four leads to the tonic F chord in bar five (Example 8).

And the ii-V/bV-I progression is jazz’s revered “tritone substitution” (Example 9).

The chart shown earlier in Example 6 is by no means complete; it simply opens the door to yet more possibilities, including cadencing on minor chords: any acceptable surprise cadence can reveal an equally acceptable substitute progression within the key of the former surprise.

But its applications are endless. Yes, as a composer or arranger you can learn to employ these colors. But often overlooked is the potential for the improvising jazz soloist, who can extemporize lines in the key of the bIII (or any other) to create tension over a basic ii-V progression, landing when ready back in the key of the I chord—whether the accompaniment adjusts to those new tones or not. You’ll hear such in the performances of many renowned soloists whose tolerance for dissonance leads to colors that are not always random chromaticism but often organized chromaticism, freeing those soloists from the bounds of otherwise-recommended scales for given chords. The following, extensive Example 10 (not published in the print edition of this article for lack of space but provided here as an additional notated and audio illustration) demonstrates how such a soloist might be thinking—even if the rhythm section is not making a single adjustment to complement the soloist's harmonic conception.

After all, if you follow the notion “you can play any note over any chord, so long as you convince me” to its logical conclusion, you arrive at “you can play any chord over any chord” as well.

Beyond the above example: if the accompanying instruments do shift some or all of their tonal centers to match in the moment the soloist's harmonic colors, the result is less dissonance between solo and comping—traded for a wildly varied set of solo changes for that chorus of the tune, inspired by the adventurousness of the soloist. Sometimes the comping instruments lead the variances, prompting the soloist to either adjust to the new harmonies or to convincingly deliver what had been diatonic solo lines now over dissonant harmonies.

With substitute progressions in play, the harmony of a standard tune can become a fountain of improvised possibilities.

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