Diminished chords are the rebels of the major scale. They can be beautiful and mysterious. They can also cause a lot of trouble. Music teachers don’t like to deal with them. (Some may not understand them). They don’t follow ‘the rules,’ or they don’t seem to. And it’s easy to get lost in rabbit holes trying to explain them. But it doesn’t have to be that way. If diminished chords are something you’re interested in playing around with, a single principle reveals a lot about how they work. That’s what I’m going to talk about.
Caveats & Technicalities:
I’m focusing on diminished 7 chords, but these principles work with any chord with “diminished” in the name. That includes minor 7b5 chords, a jazzy name for a diminished chord.
The Chord Forms:
Here are three diminished 7 chord forms.
They are movable. Once you are comfortable playing the forms, you can move them anywhere you like on the fretboard. Each of these is named by its lowest note, the note in black on the diagram. But you don’t need to know the chord’s name to use it. All you need to know is the principle that diminished chords like to move “up” a fret to the major or minor chord one fret above it. That’s it. That’s the secret of diminished chords.
An example is Bdim7 moving to C major. The lowest note in the B chord moves ‘up’ one fret to the C note. Here’s a chart showing only the lowest notes of each chord, so it’s easier to see.
And here are the complete chord charts:
The same principle works to move to minor chords too. Here’s Bdim7 moving to Cm
That’s pretty much it, the secret of diminished chords revealed!
Here’s another example using the diminished chord form with the lowest note on the sixth string. I’ll start with just the bass notes again.
And here are the full chords.
You could do the same thing moving from F#dim to Gm.
Filling in Gaps with diminished chords
Adding a diminished chord between chords whose closest notes are two frets away is a time-honored tradition. Any two chords that are two frets away from each other work. As an example, I’ll use chords from The Axis of Awesome.
The Axis of Awesome is all the major chords from a key (three chords in a row from Chord Flow) and the related minor of the key. In the key of C, that’s G, C, F, and Am.
The notes G and A are two frets away from each other. If you add a diminished chord between them, it looks like this:
F and G are two frets away from each other, and F F#dim G is pretty common too.
You could even really go for it and combine the two, creating this progression.
Like everything in music and Chord Flow, it’s good to play around and find sounds you like. (I like putting diminished chords in my songs that don’t connect to anything sometimes).
Bonus: Diminished chords and the secret of musical ‘gravity.’
A long time ago, I was sitting with my guitar teacher, and he asked me what’s the most emotional interval. (An interval is the space between two notes). His answer was one fret on the guitar. This is the same movement we’ve been exploring. Moving one fret ‘up’ from a diminished chord to another chord holds one of the secrets of music (and one of the secrets of chord flow as well). It’s like the gravity of western music. The closer any two notes are, the more they want to be together. There’s a lot to explore in this idea—more than I can delve into in this blog. But if you wanted to begin exploring on your own, you could start by looking at the chords in the key of C. There’s one diminished chord in the scale, B diminished. And it’s one fret away from the C major chord.
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