Scale Substitution

Scale substitution is an interesting way to superimpose certain tonalities over certain chords. Remember in the major scale modes page where it is written that you should play the scale that immediately corresponds to the chord, C major chord/ C major scale, C lydian chord/ C lydian scale, well, in this page we are going to contradict and have a little look at scale substitution.

Let´s imagine a C minor 7 chord vamp, here are some scale choices :

C Dorian
C Jazz Melodic Minor
C Harmonic Minor
C Natural Minor
C Minor Pentatonic

These are the more consonant choices, however, if you wanted to play less consonant and create some dissonance and play “outside” you could try playing a C minor pentatonic then move it down a semitone to B minor pentatonic; you have to be careful how you do this but here is an example using some chromatic notes:

Pentatonic Example 1

The reason for moving down to the B minor pentatonic is to create tension. One could analyse the notes of the B minor pentatonic scale in relation to the C minor 11 chord and find some strange note/chord relationships but it would probably be best to think of the scale as a temporary side step from the home key centre. The other option is to side step upwards and play the C# minor pentatonic and then resolve back to C minor pentatonic.

This type of playing was introduced by John Coltrane, it is an extension of the idea of chordal ambiguity whereby the overall quality of a chord is implicit rather than explicit giving the improviser more freedom to express multiple tonalities in the improvisation. For example, if you play a basic C minor 7 chord C Eb G Bb, the chord structure is well defined and has more stability than if you were to play C F Bb. The C F Bb voicing is a 3 note chord built on fourths, and is less stable because there is no 3rd, as a result of this you have a lot more options in choosing the tonality you want to imply.

Another option for tension is to treat the C minor 7 as a I chord and play a G altered scale, as if there was a G altered V chord present, and resolve to a C minor scale of your choice, this device is less dissonant than the previous example, but can imply forward motion, in your solo:

Pentatonic Example 2

If we take a C7 chord and look at the possible scale applications, we have the more consonant choices:

C Mixolydian (Dominant 7 Scale)
C Major Pentatonic
C Lydian Dominant
G Dorian Minor
G Minor Pentatonic

Some dissonant choices maybe the C half/whole step diminished, C altered or G altered.

Let's look at C h/w diminished for example.

The notes of the C h/w diminished scale in relation to the C mixolydian:

A#(Bb) b7
A 13
G PERFECT 5th
F# AUGMENTED 4th
E MAJOR 3rd
D#(Eb) #9
C# b9
C ROOT (from the bottom up)

The implication is the altered sound over the regular C7. With the G altered you can think of the C7 as being the modified I chord in a II V I and imply the V chord tonality over the C7; this application can really lift a solo giving yet again a kind of forward motion, but be careful how you resolve, remember there is no point of going outside if you don’t know how to come back in.

A quick note about modal jazz...

The type of jazz harmony that revolves around one or few chords is modal jazz. The concept of modal jazz is that you use one mode per chord, this can be challenging since you are restricted to the 7 different notes that make up one mode. A classic example of modal jazz is the album, ‘Kind of Blue’ by Miles Davis; you will notice the recordings illustrate modal playing, but in the solos, the temporal rule is broken,ie. the rule of one chord one mode, as many of the solos particularly by Coltrane will testify. This leads to the idea of bending the rules of modal jazz slightly and using the type of outside playing devices we have looked at.