Chord substitutions

This is a really important theme that you should be aware of right from the start. Chord substitutions make jazz sound like jazz, and they also make jazz playable.

First, chord subs to make life easier. Consider this:

Cm7, Cm9, Cm11, Cm6
C7, C9, C13, C7#11, C7b13, C7alt
C6, C69, Cmaj7, Cmaj9, Cmaj13

How long does it take to learn how to improvise over those 15 chords? Answer: not nearly as long as you think, because it's actually only 3 chords. The first important area of chord subs is simplification. When improvising, just think Cm7 for all the chords in the first row, C7 for the second row and Cmaj7 for the 3rd row. That gives you the four important chord tones for improvising, and for the rest you use your scales, your imagination and your ears, rather than trying to approach each chord symbol differently.

For comping, you can put the same relationships into reverse. If you see Dm7-G7-Cmaj7 in the chart, feel free to use any of the extensions and alterations shown above, and more, in order to make a cool and interesting accompaniment. That's what I meant about making jazz sound jazzy. Just keep your ears open when playing with others - if you play a #5 while the soloist is playing a natural 5th, you'll hear what I mean!

But there will also be times when you want to simplify when comping, because the chart shows some 7b13 chord you can't grab in a hurry, or because you want to leave the soloist plenty of space. For this it's worth learning these chord grips:

maj7 dom7 min7 dim7

Here you have minimalistic chord grips for the 4 chord types, on the top row with the root on the 6th string, on the bottom row with the root on the 5th - so with these two sets between the 3rd and 9th frets, you can play in any key. They all use only the root and the middle two strings, so it's a laid back, subtle sound. Mute the unused strings with your fretting hand. This lets you state the basics of the harmony through any tune. I find it lets me comp with confidence, knowing I always have these shapes to fall back on.

So what's happening here - why is it OK to leave out the extensions and alterations that the chart shows, and to add them when they're not in the chart? Ultimately, it's about jazz being improvised music. Unlike pop, rock and folk guitar, for a jazz tune there is no single "right" chord progression. As a jazz musician, you play it your way.

That being the case, it's fair to ask why jazz charts show extended and altered chord names at all - why not just show the basic 7th chords throughout if the player is going to be adding his own extensions and alterations anyway? There are three reasons why the full chord names get into the sheet:
  • Because the chord symbols aren't intended for the accompanist, they're intended as a hint for the soloist as to what scale he should use. C7b9 tells the soloist to use a diminished scale, C7#5 tells him to use a whole tone scale, C7#9 tells him to use an altered scale. The accompanist doesn't need to play the same alterations that the soloist is playing, that just dilutes the effect.
  • Because many jazz charts were written down by somebody transcribing off a recording rather than by the composer. They've written down exact chord voicings that the guy on the recording used. But you don't have to use those, you can find your own.
  • Because they're taking the melody into account. If the melody puts an F tone over a Cm7 chord, they might write the chord as Cm11 to explain this. That may be useful information. But when comping you don't actually need to play the 11th on the melody chorus, because that note is already there in the melody - and on the soloing choruses it's irrelevant anyway.
To round off the chord substitutions section, a brief look at going beyond extensions/alterations and playing a completely different chord to the one shown. You should be aware of some important parallels, where two chords with different names have the same notes. For example, Am7 = C6, Am9 = Cmaj7, Am7b5 = Cm6, G7b9 = Abdim7. You can substitute these freely, and when you start adding other extensions on the substitute you get some cool effects.

Another important one is C7#5 = Gb7#5, called the tritone sub because the interval between the two roots is a tritone. Try it out in a ii-V-I in C: play Dm7-G7-Cmaj7, then compare the sound of Dm7-Db7-Cmaj7. You'll hear the cool altered 7th sound, plus the satisfying sound of the bassline going down in chromatic steps. It's also very easy to find on the fretboard.

You can use these substitutions when soloing too - but don't be in too much of a hurry. Make sure you can improvise from an Am7 scale over Am7 before you try to use it over other chords!