Diminished 7th Chords.
You Know This Sound
You’ve all heard this chord sound before.
It is the chord the piano player in silent movies ALWAYS plays when something terrible, frightening, or dramatic is about to happen.
The piano player then typically plays the dim7 chord moving up in minor 3rd intervals to build to a climax.
Moral of this story: dim7 chords contain a lot of tension.
The Structure of The Dim7 Chord.
The diminished 7th chord is a symmetrical chord.
What that means, is that the 4 notes that make up a diminished chord, are all equal distance from one another, dividing the octave into a number of equal divisions.
To form a diminished chord, you stack minor 3rds.
A minor 3rd is a 3-fret distance.
If you stack 4 minor 3rds on top of one another, you cut the 12-note octave into 4 equal 3-fret parts.
For example, the notes in an Adim7 chord are:
A C Eb Gb/F#
When you stack another 3rd on top of the F#, you get A again, and the cycle just starts over again from there.
As a result: the notes in your chord shape repeat themselves every 3 frets. This explains why you can move the chord shape up and down the neck in 3 fret distances, and it is all the same chord.
For example, if I built an Adim7 chord stacking minor 3rds I get the notes:
A C Eb F#
If hit these notes at the same time I am playing an Adim7 chord
If I move that Adim7 chord shape up 3 frets, now my lowest A note moved to C, the next note C moved up to Eb, Eb moved up 3 frets to F# and the next note F# moved up to A.
This gives me the notes:
C Eb F#/Gb A
It’s an Adim7 chord again, but now with C as the lowest note.
The Tension in the Dim7 Chord
The dim7 chord has a lot of tension because of its 2 tritones. When you stack two minor 3rds, your outer 2 notes are a tritone interval, which is a highly unstable interval.
A diminished 7th chord contains two tritone intervals.
For example, in the Adim7 chord, you have the
A – Eb tritone and the C – F# tritone.
That is why this chord has a strong forward direction in a chord progression.
It wants to go (resolve) somewhere.
Every Note Can Be The Root in a Symmetrical Chord
Because of the equal distance between all the notes, diminished 7th chords don’t have a sense of “root”.
Every note in the chord is the root. An Adim7 chord is also a Cdim7, is also an Ebdim7 is also F#dim7.
So how do you know which name to give the chord if the chord can have 4 different names?
The naming of the chord is dependent upon its function within the chord progression.
This will make sense in the next section discussing the 3 uses of a diminished 7th chord.
But first off, let’s have a look at the dim7th chord shapes.
See the following video to learn the shapes.
The 3 Different Uses Of Diminished 7th Chords.
Diminished 7th chords are used in 3 specific ways in composition and songwriting.
- As passing chords
- As delayed resolution chords to I and IV
You can’t place a chromatic passing chord between the 3rd and the 4th, or between the 7th and the 8th chord in a major scale. That is where the half steps are in a major scale.
You can however delay the motion to I and IV in the scale or chord progression by preceding the expected I and IV chord by Idim7 and IVdim7.
This creates the feeling that the expected resolution to I or IV is “slowed down” or “delayed” by a dim7 chord to ultimate resolve right after to the expected chord.
- 1) ||: Cmaj7 | Fmaj7 | G7 | Cdim7 :|| Cmaj7
2) ||: Cmaj7 | Fdim7 | Fmaj7 | G7 :||
3) Cmaj7 C#dim7 | Dm7 D#dim7 | Em7 Fdim7 | Fmaj7 F#dim7 | G7 G#dim7 | Am7 A#dim7 | Bm7b5 | Cdim7 | Cmaj 7 ||
- As a substitution for V7
Anytime you have a V7 chord in a scale, you can substitute that V7 chord with a dim7 chord up a half step from the root of the V7 chord.
For example: in the key of C major, I can replace the G7 chord with an Abdim7 chord.
The reason why this works is that both these chords share the same notes.
G7 = G B D F
Abdim7 = Ab B D F
In other words: an Abdim7 chord is a G7b9 chord minus the G root.
- 1) ||: Cmaj7 | Am7 | Fmaj7 | G7b9 (=Abdim7) :||
2) The Fdim7 chords at the end of the song “Tears In The Rain” (Are all substitutions for E7 chords, which is the V chord in the song’s key of Am)
Whenever you have 2 consecutive diatonic chords in a chord progression, that are a whole step apart, you can place a diminished 7th chord in between those 2 chords as a chromatic passing chord.
The chromatic bass motion connecting 3 consecutive chords, creates a feeling of forward motion and direction in the chord progression.
- Cmaj7 C#dim7 | Dm7 D#dim7 | Em7 | Fmaj7 F#dim7 | G7 G#dim7 | Am7 A#dim7 | Bm7b5 ||
All this probably might make more sense if you can also hear it in the following video:
If you haven’t used the dim7 chord yet, have fun adding them to your songs.
Knowing about these chords gives you yet another tool to create different textures and colors for your songs.
Moreover: the unstable nature of the chord can really enhance the flow of your storytelling in your songs, giving you yet another tool to create stronger forward motion in songs that are asking for it.
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