The Diminished 7 Chords

The diminished 7 chord is a very unique and useful chord. Some of us older folk remember the Mighty Mouse cartoons with the girl tied to the railroad tracks by the villain while the locomotive speeds down the tracks headed toward the damsel in distress. We hear the diminished 7 chord in the background ascending chromatically bringing us to the edge of our chairs hoping Mighty Mouse will come to save the day. And, of course he does and the diminished 7 chord resolves to major chord and we lay back in our chairs relieved that all is well.

Well, creating tension for trains and suspense movies is one way to use the diminished 7 chord; however, there is much more the guitarist can do with them. The diminished 7 chord is used in jazz and blues extensively.

The first time a guitar student fingers a diminished 7 chord, he might be tempted to move on to other things because of the sound. It sounds dissonant and, at first, it might not seem to be a useful chord. However, keep in mind that it needs to be heard in context with other chords to make sense. The chord it’s coming from and the chord it’s going to makes all the difference in the world.
The diminished 7 chord is rarely played more than two beats in a measure. The most common use of the diminished 7 chord in jazz is to replace the vi chord in the I, vi, ii, V chord progression with the ♭ii dim7 chord. For example, the I, vi, ii, V chord progression in the key of C is CMaj7, Am7, Dm7, and G7. Using the substitute, the progression is CMaj7, C#dim7, Dm7, and G7. The diagrams below illustrate the chords. Give each chord 2 beats.


The Blues

The diminished 7 is also used in blues. The IV chord in the I, IV, V chord progression can be substituted with the #IV dim7 as illustrated in the chord diagrams below. Give each chord diagram four beats and you’ll have the twelve bar blues.


The Uniqueness

The diminished 7 chord is unique for several reasons. First, it is symmetrical. The diminished 7 chord has four intervals: The 1, the ♭3, the ♭5, and a ♭♭7 (♭♭7 is the same as a 6). These intervals are all 1½ tones apart. That is, 1 to b3 is a minor third distance (1 ½ tones). The distance from ♭3 to ♭5 is also 1½ tones. The same is true for the ♭5 to the ♭♭7. This is why I say the diminished 7 is symmetrical. Second, any note of the chord can be the root. For example,  Cdim7, is also  G♭ dim7,  Adim7, and  E♭ dim7. So, by knowing one dim7 chord you actually know four. The third reason the dim7 is unique is because the chord inverts every three frets (every minor third). In other words, if I take Cdim7 and slide it up the fret board three frets I have the same four notes — the same chord. I simply played an inversion or a different voicing of the same chord. Slide up three more frets and it inverts again. In the illustration below, we have four voicings of the same chord.


The Three Biggies

Although there are many ways to play any chord, there are three fingerings that I use most of the time. Which fingering of the diminished chord I use depends on the chord before and after it. The three fingerings are seen in the chord diagrams below. I used the key of G but the fingerings are movable and work in every key.


It Don’t Mean A Thing If It Ain’t Got That Swing!

The progressions below is used in hundreds of songs from the swing era.

If I’m playing chords with the root on the sixth string, then I’d play the chords like this:

If I’m playing chords with the root on the fifth string, then I’d probably do this:

If the root is on the fourth, then I’d play this:



If the song keeps repeating the progression, then I’d use inversions to make it more interesting. Keep in mind that F#dim7 and Adim7 are the same. I usually name the dim7 by the lowest note as shown in the following chord diagrams but any note in the chord can be a root note. In essence, you get four chords for the price of one. What a great deal! :



Another way to get your inversion is to go up a tritone. The tritone or the ♭5 is the note that is exactly half way to the octave. Below I illustrate tritone inversions:

I hope this article helps shed some light on using the diminished 7 chords. You have heard the expression, No Man is an island. Here is one for musicians, No chord is an island. Chords work when they are in context with other chords.


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