Diminished, Half-Diminished, and Augmented Chords
Diminished chords naturally occur on the leading tone (subtonic) of a major scale. For example, in the key of C major, a diminished chord is rooted on B, the seventh scale degree. The diminished chord contains a double minor third interval. In other words, two minor thirds are stacked on top of each other to create the diminished chord quality. A B-diminished chord contains the intervals B to D (minor third) and D to F (minor third). If it were a minor chord, the F would be sharp.
A B-diminished chord is shown to you in FIGURE 6-9. As you will see, a circle is used to indicate the chord quality.
FIGURE 6-9: B Diminished Chord
Diminished seven chords are typically used as a substitute for V chords. As unstable chords, they naturally lean in the direction of the tonic. A diminished seven stacks another minor third interval on top of the root, making the interval between the root and seventh enharmonically the same as a major sixth. For example, a B dim7 chord contains an A-flat on top. If written as a G-sharp, the interval will be a major sixth.
The diminished chord gets its name from the interval created between the root and the flatted fifth. As you might guess, this interval between these two scale degrees is a diminished fifth.
Don't be confused by enharmonic naming. Just remember that a diminished seventh chord contains three stacked minor third intervals. Also, bear in mind that if you wish to use a diminished triad in place of a five chord, you might instead choose a diminished seven chord as it is more colorful. The diminished seven is shown in FIGURE 6-10.
FIGURE 6-10: Diminished Seven Chord
In FIGURE 6-11, the diminished seven chord is put to use in a simple chord progression. In this progression, the diminished seven and a flatted fifth are used to alter what could be a minor ii chord into a diminished seventh chord. By altering the perfect fifth of the chord to a flatted fifth, the diminished triad reveals itself. The staggered C-flat completes the picture by adding a diminished seventh on top.
FIGURE 6-11: Using a Diminished Seven Chord
The half-diminished chord is a rather beautiful, impressionistic chord that can be used in a variety of ways. It is mostly used in modern jazz and European classical music (late romantic and twentieth-century periods). However, it can be applied to pop and rock music, adding a resplendent glow to otherwise stock chord progressions. For example, jazz-rock groups like Steely Dan might use this chord as a fancy minor ii. In this case, a V and a I chord usually follow suit.
Often spelled out as a minor seven-flat five, the half-diminished chord contains most of the same notes as a full-diminished seventh chord. The exception lies in the seventh itself. Instead of stacked minor thirds, the half diminished contains a major third on top. For example, a B half diminished contains the notes B, D, F, and A. The relationship between F and A is a major third. The half-diminished chord is notated in FIGURE 6-12. As you will see, the symbol for half diminished is a circle with a line or slash through it.
FIGURE 6-12: Half-Diminished Chord
To create a fancy version of a standard ii–V–I chord progression, you can alter the minor ii chord to become a half diminished. This kind of harmonic twist is common in jazz. FIGURE 6-13 shows one example of how to do this.
FIGURE 6-13: Using a Half-Diminished Chord
The augmented chord is a major triad with a sharp five. For example, a C-augmented chord would contain the notes C, E, and G-sharp. Enharmonically, this G-sharp is also an A-flat. As an A-flat, this interval would be called a flatted thirteenth. Like the half-diminished chord, the augmented chord is used primarily in jazz and contemporary classical, but it could also have applications in rock and pop. You will definitely see and hear it used in the blues examples found later in the book. FIGURE 6-14 shows you a C-augmented chord and a C-augmented seven chord. A C-augmented chord is usually written as C7#5 or C+7. The “+” symbol indicates the presence of a sharp five. Usually, augmented seven chords are used to spice up V chords.
FIGURE 6-14: C-Augmented and C-Augmented Seven Chords
FIGURE 6-15 shows you a fancy version of a standard ii–V–I chord progression. In this figure, the V chord has been altered to become an augmented seven chord. Listen to how the augmented chord changes the color and feel of this stock progression.
FIGURE 6-15: Using an Augmented Seven Chord