TRITONE SUBSTITUTION
For each Dominant Seventh chord there is a substitute Dominant Seventh chord which can be found by moving up or down a 'tritone' from the root of the given chord. Example:-
C7+'tone'+ 'tone'+ 'tone'= Gb7
This substitution has in its structure the same 'tritone' notes (the major 3rd. and the b7) as the given Dominant Seventh chord, but their roles are reversed.
The 'E' is the major third in C7 - the minor 7th. in Gb7.
The 'Bb' is the minor seventh in C7 - the major third in Gb7.
Although the tritone substitution is an option, it should not be used to excess. It does however add to the related scales which are available for improvisation. Hence the mixolydian of the F major scale and the mixolydian of the B major scale are both available to 'blow off'.
The following are examples of the opening four bars of Jerome Kern's 'All The Things You Are'.
the standard chords with bars three and four as Eb7 moving directly to Abmaj7.
Example 2
click on the manuscript to hear the sequence
bars three and four, the Eb7 - Abmaj7 is changed to A7 - Abmaj7.
Example 3
click on the manuscript to hear the sequence
the change is further developed with Em7 - A7 - Abmaj7.
This is typical of the way in which Tritone substitutions are used.
There are many other substitutions and embellishments which are used in Jazz. To list them all would be impossible and not desirable, since part of the joy of Jazz is discovering for oneself new and old variations which are used by the great exponents of the creative art.
Altered Chords, licks, turnarounds and bits and pieces.
Harmony can be enriched and subtle qualities can be derived by adding to or altering in various ways the structure of a chord. The basic major seventh chord, for example, may be enriched by adding the 9th, 11th and thirteenth tones to the chord.