When I was younger and first getting into learning about harmony I was always fascinated in particular by certain jazz pianists and their ability to string long complex chord sequences together, drifting in and out of original key with ease. This is what I became to understand as chord substitution, and is done to harmonic variety and interest to a piece.

The original melody was still embedded in what they were doing, but its was constantly being re-contextualised, pushed and pulled out of focus. Pianists like Bill Evans, McCoy Tyner, Mal Waldron, George Shearing, Kenny Barron, Chick Corea and latterly Brad Mehldau were masters of this craft in my eyes. What they were really doing was actually quite structured, quite literally swapping the chords or “changes” of the original tune with logical alternatives.

Mal Waldron.

The substitutions may have a quality and degree of function in common with the original chord, and often only differs by one or two notes, or they may be far more off the wall, flirting with other keys and modes temporarily, then with deft skill brought back to the home tonal centre.

This article is meant to serve as a basic introduction to substitutions. I’m really just covering the theory behind it, using them tastefully is an art in itself.

The most important things to remember is taste, context, and reference (to the melody). It’s no good throwing obnoxious heavily extended altered chords at a sensitive ballad or going on some modal odyssey during Fly me to the Moon (or perhaps there is? Sure someone can make it work).

So, let’s start at the beginning.

Consonance and Dissonance

Nearly all european and western music conforms to some basic rules. You may seek to break them. You may think what you do is different and you’re oh-so avant garde and post modern, but the chances are you music still relies on the tried and tested constructs of consonance and dissonance, or to put it differently; tension and relief.

Western harmony is derived from the harmonic series (more on this at a later date) which comes from the natural physical phenomena of vibrating strings at different lengths, and whilst I’m not here to illustrate that the point I am trying to make is that although music is very subjective – some constants should be understood.

The V – I movement (chord 5 to chord 1 in a major or minor scale) is the strongest in western harmony. In the key of C major this would be G to C, or G7 to C. There are other ways of finishing chord sequences using different cadences, but this movement has a gravitational pull.

McCoy Tyner.

If you play a melody and stop three quarters of the way in, you will naturally fill in the gaps with your mind – our ear seeks to resolve melodies, harmonies and bass lines. Of course, you don’t have to finish your piece of the tonic, and there are various ways to get from skin the proverbial cat, but knowing about tonal centres and keys can help when exploring chord substitutions.

For example, if you’re in the key of C, we might be able to dabble in various related keys (F major, G major, A minor) we might be able to sideslip into more arbitrary-sounding keys (Db major, B major, Gb major) but we need to return back to our goal key in order to put a bow on our progression, and the best re-harmonizers know this.

Common Substitutions

One of the easiest ways to quickly start modifying your chord changes is by swapping two chords that share similar notes. Staying with our example key of C major, you’ll find there’s a plethora of chords that share two notes. If you’re unfamiliar with chord naming conventions, please read this.

Chord Name Symbol Notes Substitutions
C major 7
C∆7
C E G B
E-7, A-7
D minor 7
D-7
D F A C
F∆7, Bø
E minor 7
E-7
E G B D
G7, C∆7
F major 7
F∆7
F A C E
A-7, D-7
G dominant 7
G7
G B D F
Bø, E-7
A minor 7
A-7
A C E G
C∆7, F∆7
B minor 7 flat 5
B D F A
D-7, G7

The net result is you can really interchange most of these chords freely without compromising the harmonic direction or movement of a piece.

Of course it’s not that sample and you have to be aware of the melody. If the downbeat of the melody is a C, then A minor would work fine, but an E minor not so much (E minor has no C in it).

However this is only really the beginning. We can further extend these chords with richer voicings using 9s, 11s, 13s and altered extensions. We can even swap major chords for minor and vice versa.

Anticipating Changes

Another common technique is to anticipate the next chord by preparing it with a leading chord. If you remember above we discussed the pull of the V – I movement, this means we can prepare for the next chord using it’s V chord or a diminished or half-diminished passing chord.

Let’s look at (probably) the most famous string of eight notes there has ever been; jazz cliche The Lick (which you can read more about here, from Ethan Hein’s blog).

Here’s the lick in A minor (the relative minor key to C major), pretty simple stuff.

Let’s start by using the V and i chords in A minor, E7 and A minor respectively. This gives the phrase natural bookends. If we chose another chord to finish on, it wouldn’t sound quite as compartmentalized, and needing additional notes or harmonies to finish it off.

We can build on this by preparing for the E7. In the key of E the V would be B, but since we’re in A minor let’s stick to the diatonic chords found in that key. The B chord in A minor is a Bº (B D F Ab), together this completes a ii V i progression in A minor.

Tritones

I’m going to cover tritone substitutions in a lot more depth elsewhere, but the principle is worth discussing. A tritone is an interval composed of three (tri) tones, or six semitones if you prefer to think of it that way. So the tritone of G would be Db, C would be Gb, B would be F, A would be Eb and so on.

A common technique is to swap out the V chord in a ii V I progression with its tritone buddy, leaving you with a chromatic movement. In C major, we’d see D minor, G7, C major become D minor, Db7, C major.

This can be taken a step further, let’s look at a iii VI ii V I (E minor, A7, D minor, G7, C major), by substituting the A7 and G7 we are left with E minor, Eb7, D minor, Db7, C major. One Note Samba is a great example of this type of harmony:

Abide With Me

Now let’s apply a few of the above discussed harmonic techniques to something. I’ve taken the first eight bars to Abide with Me, as it’s not only a beautiful hymn but has some tasty chords. Here’s John Coltrane and Thelonious Monk’s Septet performing it in 1957:

Here’s the original changes in C major. Note our melody in relationships to the chords – it’s important note to drastically change the top line as it’s so powerful.

N.B I’m using the tenor suboctave clef on the bottom stave.

The first thing I’m going to do is fill it out with some jazzier voicings of the chords. All I’m doing is adding the seventh diatonic note of each chord (except in bar 8 where I’ve used the sixth note) and changing the inversion so the melody is on the top and the chord fills out underneath it.

I’ve snuck in a cheeky Bº chord in bar 3, leading from the G7 to the C∆. Bº is harmonically very close to the G7, in-fact you could interpret it is a G7(b9)/B if you wanted to.

In addition I’ve also anticipated the C chord in bar 7 with a G7, meaning we now have a ii V I progression before the D7 (V of G major) anticipates the final chord. We could have also substituted the G7 in bar 1 for an E7 which anticipates the A-7 in the next bar – as you can see, there’s a plethora of options.

N.B I’ve switched to the more conventional treble and bass clef.

Next I’m going to use diminished chords to join the dots, trying to channel my best Bill Evans. In bars 1 to 2, the Dº7 acts as a passing chord between the C∆/E  (C major 7 with an E in the bass, known as a slash chord) and the C6.

In bars 3 to 4 we use an Abº7 and cadence on the vi (A-9), which is sort of an interrupted or deceptive cadence (V – vi), as the Abº7 is a common substitution for G7. Bars 5 to 6 sees us start on an Eº7 (not something I often do), and the basslines leads diatonically to the F∆/A (E, F, G, A).

Lastly in bars 7 and 8 we use the same styled diatonic and chromatic movement to reach our goal of the new key, G major, preparing it with an F#º7.

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