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diminished seventh chord symmetry

1,624 views · Published 1 February 2016 · 8:33 · Indexed 1 November 2026

Channel: New Secret Guitar Teacher · 2016 · Music

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Diminished chords. How the diminished seventh gets its symmetry. Chord symmetry explained.

From the Secret Guitar Teacher Site: http://www.secretguitarteacher.com/youtube/ssb.php?lp_id=1119

Video script:
We took a look at the Diminished Seventh Chords right at the start of the Secret Sound Bite Advanced Series. But in this lesson we'll bring it into line with our discussion of symmetrical chords in general and also look at how its symmetrical properties open up a couple of fun ways it can be used.

The Diminished Seventh Chord occurs naturally when we harmonize the Seventh Degree of the Harmonic Minor Scale. Remember, the Harmonic Minor Scale - is the minor scale that retains the natural 7th so its formula is b3 b7.                        
 
So let's start by looking at these four  Diminished Seventh Chords, shown here in their natural Habitat. I have shown the four diminished seventh chords that occur on the 7th degree of the Harmonic minor scales in the keys of A minor, C minor, Eb minor and Gb minor. 

Again, complex chord signatures tend to make it very hard to spot any significant connection between these four chords. Until we zoom in and work out the names of the notes in each chord. Which I have done here on the left by applying the diminished seventh formula 1 b3 b5 bb7 to the major scale of the root note of each of the four chords. And on the right I have listed the enharmonic equivalents that show up when we do this. So now we can clearly see that all four of these chords contain the same four notes.                                             

Four chords of the same type proving to be synonyms - there must be some serious symmetry involved! 

And as in the last lesson, a great way to reveal the symmetry is to plot the notes against the chromatic scale like this. And we can see that the notes are all the same distance from each other - we can call this distance 3 half steps, 3 semitones, a tone and a half or most usefully in the long run simply think of it as a Minor 3rd.

This makes the Diminished 7th chord the ideal choice for providing a sound effect whenever you want to show a smooth gradual transition from one thing to another. Which is why you often hear it used in the background music for cartoons where, for example Tom is Chasing Jerry up a ladder. Coming back down the ladder I can even use all three different diminished 7th chords to good effect chromatically like this.

Another fun thing the symmetry of these chords allows us to do is to string together a whole bunch of them wherever we see any dim7 chord called for in a chord sequence.

For example, here's the verse from a version of the Jazz Blues Standard: Ain't Nobody's Business  in place of the single Fdim7 chord that comes after the G I have the option to string together as many dim7 chords as I can fit in - as long as they are spaced a minor third apart.You may have heard me do a similar thing with the Song Nobody Knows You When You are Down and Out.
                  
So look out for opportunities to play with that idea...like me, you may be tempted to overdo it at first...fine when you are working out ideas...just  remember to rein it in a little in actual performance!

In the next lesson, we'll conclude our tour of symmetrical chords by taking a look at the Augmented chord and again I'll be showing you a few fun applications of that.

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