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followed by the same sequence starting from Em. Notice that an augmented chord is made up of two intervals of two
tones (full steps) each. If you try to add another one, you come full circle: in C, the note two tones above G# is...
C. Therefore, the augmented chord cannot be added to by the method which increases the complexity of other
chords.
Diminished/Diminished Seventh Chords
The diminished triad (C Eb Gb) is almost never used on its own. Instead, another note one-and-a-half tones above is
added to create a diminished seventh: C Eb Gb Bbb (B double-flat = A in pitch). In sound, this is close to a dominant
seventh chord. If we change C Eb Gb Bbb enharmonically (using alternate names for the same notes) to C Eb F# A,
the Eb has to drop only one semitone (half-step) to D to make a D7 chord. That's why this chord has a highly
ambiguous quality.
As with the augmented chord, you don't want to stay on a diminished seventh for long. It is the musical equivalent of
one of those strange particles in sub-atomic physics – the sort that are in six different places and/or six different
times at once. The diminished seventh is a mutant offspring of the minor chord, whose main employment is as a
doorway between different keys.
Each note in a diminished seventh can be regarded as the root, so each shape has multiple names. Bizarre, isn't it? I
guess you won't be surprised if I tell you that the number of hit singles with diminished sevenths is pretty small. It
sometimes turns up in Meatloaf numbers, to assist that air of faded grandeur. David Bowie put several in the chorus
of 'Quicksand', thus causing a generation of guitar tyros to gnash their teeth because they could not figure out what
the hell was going on. But it is popular in jazz. You have been warned....
Dimished seventh chord shapes