Synthetic Mode - Symmetric Diminished and Inverse Symmetric Diminished Scales

Symmetric Diminished and Inverse Symmetric Diminished Scales

These two modes, which are mirror image to each other and are also transpositions of each other, are created by dividing the octave into four equal parts and adding an interval of either half a step or a whole step to each resulting note. As such, they are both symmetric scales and are used in diminished context, albeit in a different manner. They are also the result of superimposing two diminished seventh chords set either half a step or a whole step from each other.

The symmetric diminished scale, also known as "half-whole", goes as follows:

1 ♭2 ♯2 3 ♯4 5 6 ♭7

It can be applied to a dominant chord, the root of which can be equally transposed to any note of the diminished seventh chord built on the root. For example, this scale starting on C (C D♭ D♯ E F♯ G A B♭) can be applied to either C7, A7, F♯7 or E♭7.

The inverse symmetric diminished scale, also known as "whole-half", goes as follows:

1 2 ♭3 4 ♭5 ♭6 7 (♮)7

This scale is used as the chord scale for the diminished seventh chord. Naturally, as the diminished seventh chord is symmetric and therefore, sounds the same when started from either note, the same goes for the scale. For example, this scale starting on C (C D E♭ F G♭ A♭ B B(♮)) can be applied to Co7, which in turn is enharmonically equivalent to Ao7, F♯o7 or E♭o7. Note that the diminished chord is always tense and its seventh is double flattened (7); therefore, only in diminished context can a ♭6 (or ♭13) be played simultaneously with what is the enharmonic equivalent of a ♮6 (voiced only a major seventh above it or a minor second below it, the latter being only valid in piano voicings, but never a minor ninth below it). It is also the only context where the major seventh is considered a tension, rather than a chord tone.