Reharmonization Lesson for Jazz Piano

I was recently asked:

“Is there any theory I need to know to use reharmonization in my Jazz piano playing?”

Here's my answer:

‘Reharmonization’ means to ‘change the chords’.

So when you play a song from your real book - you have the freedom to change the chords.

If the song book says ‘C minor 7’ - you could change it to something else, like ‘C minor 7 b5’ (subtle), or ‘C major 7’ (interesting - ‘I see what you did there’), or to something completely out there - ‘Ab7#11’…

Now let me debunk a myth:

It is rare to reharmonize any more than 2 chords in a song…

Yes, reharmonization is often used by jazz musicians - but you wouldn’t want to change every chord in the song (in fact that wouldn’t be desirable for most listeners - they still want to hear the original tune most of the time)…

(Occasionally you might hear a complete reharmonization - where a jazz pianist embarks on changing virtually every chord in the song, but this is more of an extreme challenge / exercise on their part. Normally reharmonization is only applied to one or two chords per song.

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Working backwards:

Most reharmonization techniques work by choosing a ‘target chord’ in the music (any significant sounding chord you like in the song) - and then to PRECEDE that chord with a new chord that you add in yourself…

That means you’re working backwards and creating a strong resolution to that ‘target chord’…

For example, if there’s a C major 7 chord in the music - you could work backwards and add in a chord that will resolve more strongly to C major 7:

G7 - C maj 7 would be the most basic reharm. (because all dominant 7 (V7) chords want to resolve down a 5th)…

Db7 - C maj 7 would be using ‘tritone substitution’ to preceded your target chord. Just count up a half-step from C major 7 and play a V7 chord (Db7)…

And Bº7 - C maj 7 would be another strong resolution. Just count down a half-step from your target chord and play a dim 7 chord (a stack of minor 3rds: B D F Ab)…

Diminished 7 chords are full of tension and they want to resolve up a half-step to a major 7 or minor 7 chord - so this always sounds great.

Note: B dim 7 sounds very similar to G7b9 - it has the same notes (just missing G in the bass) - and its notes want to resolve the same way that G7b9 wants to resolve - to C major 7 or C minor 7.

NOTE: The main reason I change a song’s chords is that I want more chord changes. So usually I find myself adding in new chords (around the song’s original chords), rather than replacing / substituting the chords that are already there (although this can be done too).

Free Resource: Download my 'Chord Symbol Reference Guide'

Shows you all types of Jazz chord notated clearly on one page - including 7ths, 9ths, 11ths, 13ths.

Working forwards:

The other direction you can think is forwards.

So once you’ve played a chord - you can add new chords after it:

The most common ‘follow on’ reharm. I use is this:

After a C minor 7 chord is played - you can tag on an F7 chord after it…

Doing this turns C min 7 into the ii chord of a ii-V progression, and F7 is the V7 chord (this would be a ii-V in Bb major)…

So it’s simple - when you see a minor 7 chord held for 4 beats - just shorten it to 2 beats and follow it with a dominant 7 (V7) chord a 4th above…

Another common reharm I use is for major 7 chords:

Let’s say you see a C major 7 chord held for 2 bars (that’s 8 beats):

Turn it into this:

C major - D min 7 - E min 7 - D min 7 (each chord held for 2 beats).

This pattern turns the major 7 chord into a I-ii-iii-ii progression - which adds movement when I need more energy in a song I’m playing…

Again - the #1 reason I change a song’s chords is to add in extra chords for more movement. As a solo jazz piano player I don’t have a rhythm section or a singer to keep the music moving - and some songs don’t translate well to solo piano as they are, so that’s normally why I add in new chords myself.

Important: Tweaking the melody

When you change a chord, you change the scale that should be played above it.

So if there’s a melody that’s being played above your new chords, you’ll sometimes need to tweak the notes so that they fit with the new chord and its scale…

By ‘tweak’ I mean flatten or sharpen any notes that don’t belong in the new scale.

“Which scale do I play?”

A simple way to figure out which scale you should play above any chord is what I call the ‘chord tone + whole-step’ technique:

Start with the 4 chord tones of the chord (that’s the 1 3 5 7) - and then add a whole-step above each of these to find the remaining notes (9 11 13):

So if you have a C minor 7 chord - start with its chord tones (C Eb G Bb).

Then add a whole-step above these notes and you get C D Eb F G A Bb - which is C dorian scale.

Or if you have a C dim 7 chord - start with the 4 chord tones: C Eb Gb A.

Then add a whole-step to each of these notes = C D Eb F Gb Ab A B - and you end up playing C diminished scale.

So if the song’s melody doesn’t fit with your new scale - just tweak any dissonant notes up or down a half-step so that it fits with the new chord’s scale.

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