Chord Substitution

chord-substitution

Chord Substitution

Substitute that chord!

In the last blog, I spoke about how to substitute triads when composing melodies or improvising.

To make a long story short, the trick was to play three different triads off a chord.

In G major, G being chord I, we get G B D as our first triad, building a triad from the note B (chord III) we play the notes B D F# , in relation to G this is 3, 5, 7. This meant we got a maj7 sounding melody.

Going even further, from the D (chord V) we got D F# A, in relation to G, this is 5, 7, 9. We now get a maj9 sound.

This is all very useful stuff and should be practised extensively if you want to get into jazz since this is how those guys actually think about it.

In this blog post, I’d like to continue on this concept but instead of using triads to find melodies, let’s look at what happens when we substitute a whole chord!

Call It Stormy Monday


In ‘Call It Stormy Monday’, Sandy substitutes the G7 with a Bm7b5, why does this work?

If G is seen as chord V, then chord VII would be a Bm7b5.

In the same way, as a Bm triad created a maj7 sound over a G chord, a Bm7b5 creates a dom9 sound over a G root.

G triad: G B D
G7: G B D F
G9: G B D F A
Bm7b5: B D F A

As you can see above, the Bm7b5 and the G9 contain almost the same notes!

These type of substitutions will always work as long as you know what number the chord you play has.

The rule is always to start the substitution on the 3rd of the chord.

Tritone Substitution

I’ve been getting back into my jazz playing lately and a song that got me hooked for the last few days is ‘A Night In Tunisia’, a bebop classic by Dizzie Gillespie.

‘A Night In Tunisia’ is often seen as a benchmark song for jazz players since it is fast and contain a seemingly new progression in the Eb7Dm.

The sharp-eyed student would instantly notice that Ebmaj7 – Dm would have been an obvious IV – III and Lydian and Phrygian would have been perfect, but Eb7 complete throws this out the window, so what is it?

It’s a tritone substitution, bear with me…

Imagine that the Dm is chord VI, and the chord leading to this is a modified III chord, so IIIx, this would be A7 – Dm, very common movement, happens all the time.

Altered chords

In order to get tritone substitution you first have to understand what an altered chord is.

An altered chord is a dom7 chord containing one or several of these intervals: b5, #5, b9, #9.

By adding these notes you get more tension, more pull towards the VI chord. For example, A7b9 would include the note Bb, which is a semitone away from A, a note of the Dm chord.

The more semitones, the more tension and pull towards the next chord.

Just like we did when we substituted triads and got bigger sounding chords and melodies we can tritone substitute a dom7 chord.

A7: A C# E G
A7b5b9 A C# Eb G Bb
Eb7: Eb G Bb C#

Eb is a tritone (#4 or b5) away from A, so if we play an Eb7 instead of building a full altered chord we hit all those important altered notes!

Check again, A7b5b9 would have Eb and Bb as the two altered notes. This is the root and 5th of an Eb. The remaining two notes, the C# and the G are the 3rd and b7 of the A7 chord.

Summary

Tritone substitution or any substitution for that matter take the actual extension of a chord and highlight it.

This could be done to both melody and chords.

In ‘Call It Stormy Monday’, we substitute a G7 with a Bm7b5 to get a dom9 sound.

In ‘A Night In Tunisia’, we tritone substitute an A7 with an Eb7 to get an altered sound.

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