Enhance Your Harmonies with Jazz Chord Substitution
Jazz Chord Substitution – the mere name elicits an aura of mysterious and arcane music theory beyond the comprehension of mere mortals. But in fact it is simple enough. What were are dealing with here is the technique of Reharmonisation – changing the chords of a composition in order to create a more interesting arrangement.
The term chord substitution can be a little misleading. There are actually two different methods that are described as chord substitution
- Replacing the original chord with a substitute
- Adding additional chords while retaining the original chords
The second technique might well be described as chord addition. However, in practice, both methods are implied in the term chord substitution. Consider the example below:
This is an example of true chord substitution. In the second example, the Db7 has replaced the G7 in what is known as Tritone Substitution. Basically, Db7 will resolve strongly to C in the same way as G7 will.
This second example illustrate chord addition. In the second bar, a Dm7 (ii chord) is added on the first beat, and the G7 (V chord) is compressed into a single beat. The Dm7 (ii chord) is derived from the G7 (V chord) using a simple rule.
any dominant 7 chord can be preceded by a minor 7 chord with a root that is a fourth lower
This is one of the applications of the cycle of fourth / cycle of fifths
This chart demonstrates the full range of chords available in a given major or minor key using the technique of tonicisation (temporarily establishing an alternative tone centre within the key – a “mini-modulation” for a short duration). This technique is used extensively in Jazz and Classical music to expand the range of the major/minor system to it’s utmost. The chart below can be used to facilitate composition and reharmonisation, both in the considered and ad-hoc sense s(e.g. scoring a composition/arrangement vs spontaneous chord substitution in Jazz Improvisation). This harmonic technique can be expanded to any genre!
The following classes (functions) of additional chords are used:
1 – Borrowed chords from the parallel major or minor key
It is more common to borrow chords from the minor to enhance the major key than vice versa.
e.g. Dm7b5 and G7b9 resolving to Cma7 in the key of C major
2 – Secondary Dominants and their tritone substitutes (“V” & “bII” function)
e.g. D7 (Secondary Dominant) and Ab7 (Tritone Substitute), resolving to G in key of C major
3 – Secondary Supertonics (“iim7 & iim7b5” function)
e.g. F#m7 to resolve to B7 to Em in key of C
4- Secondary Subdominants (“IV & iv” function)
also known as borrowed chords – “borrowed” from the key’s parallel major/ minor scale counterpart
e.g. Fm in key of C or F in key of C minor