I remember my first encounter with a diminished chord. I'd set myself the task of memorizing every shape in Mel Bay's Big Fat Book o' Chords, even though I had no clue what "G7" actually meant. I plugged along anyway and eventually got to "Gdim", set my fingers up as the diagram said to and - strum - huh? What was that? Checked the diagram again...yup. I guess that's it. Whatever.

I bumped into it again on George Harrison's My Sweet Lord and later on Floyd's Brain Damage. Still didn't get it but hey, it sounds right - diminished it is. Metalheads might be more familiar with Yngwe's superhuman diminished arpeggios. We've all heard it somewhere but if you haven't really explored it you're missing out on one of the most useful scales around.

Hang with me if the theory part seems hairy. You'll be glad you did. You only have to understand it, you don't have to remember it. Everything gets really simple at the end.

First, some basics. The diminished scale is a symmetrical scale based on alternating whole and half steps. It has 8 notes per octave, not 7. Adim (w-h) looks like this:

A B C D Eb F Gb Ab (A)

A whole-half diminished scale has one "mode", the half-whole diminished scale. Adim (w-h) is related to Bdim (h-w):

B C D Eb F Gb Ab A (B)

Dim7 chords are stacks of minor 3rds. Adim7 looks like this:

A C Eb Gb

Cool Fact #1: Because of its symmetrical construction, there are only 3 diminished scales/chords. Look at the Adim7 above. A minor 3rd up from C is Eb, a minor 3rd up from Eb is Gb, a minor 3rd up from Gb is Bbb (A). Every note is potentially the root and the chord "self inverts". You get four chords for the price of one.

Now look at that Adim scale again. Ascending in 3rds, our I, III, V, and VII chords are the interchangeable A/C/Eb/Gbdim7. Looking at our scale, we have F available. F A C Eb = F7. What else is in there? Gb, the b9 of F, G# (Ab), the +9 of F. What about B? F7#11? How about F13? It's all in there. Wow.

But we're still not done yet, F Ab C Eb = Fm7. What about that B? F Ab Cb (B) Eb = Fm7b5.

Let's recap: obviously, we could use this Adim scale for A/C/Eb/Gbdim7. What else can we use it for? F7, F7b9, F7#9, F7#11, F13, Fm7 and Fm7b5. Anything else? U-bet!

Cool Fact #2: You can use this Adim scale for all of the above chords with Ab, B, or D as the root. Four for the price of one? How about 28? See what I mean by super-useful?

OK, now diminished is never going to be our "go-to" scale for a plain m7 chord so let's look at the big ones: dominants (dim7s) and m7b5s. Technically, we use a whole-half diminished for a dominant and a half- whole for a m7b5. Now...wait a minute, what happened to Low-Rent? How am I going to remember all this?

Cool Fact #3: YOU DON"T HAVE TO!

Here are some diminished arpeggios. Any note can be the root! Remember, these are all movable and if you move them up or down a minor 3rd you're still in the same scale. Four for the price of one again.



So here's the deal. To play over a dominant:

1. Play the diminished arpeggio from the 3 of the chord (F7=Adim etc.)
2. All the other scale tones are a half-step BELOW the chord tones.

(OK, you could also say "play the diminished a half step up from the root." If that works for you, fine, but playing from the 3 both ENcourages you to play 3 and b7 and DIScourages you from ending your lines on b9. You really don't want to play F# over F7 for too long, do you?)

To play over a m7b5:

1. Play the diminished arpeggio from the root.
2. All the other scale tones are a half-step ABOVE the chord tones.

That's it. See, I told you it would be simple in the end. So here's a groove to get you started exploring diminished sounds. It's a 12-bar blues in Bb. Use Ddim for Bb, Edim for Eb (yeah, I'm breaking one of my "rules"), and Adim for F. Try playing first with only chord tones, then add scale tones, then mix the diminished lines with some of your regular blues lines. Pay special attention to the tritones that define the chords. How do they relate to each other? Once you start digging the diminished scale you'll wonder how you ever got along without it. All for now. More to come. Enjoy.