# Guitar Lesson – Music Theory Part 6.7.2 – diminished

This is part 6.7.2 which is a continuation on the discussion on “7”. The reason why this is in a separate post is because, quite frankly, I forgot.  And this is also a continuation on triads where we talked about how the diminished chord is what you’d get if you built the triad starting with the 7-note on the scale.

In this case, we’re looking at the 2 diminished chords: Half-Diminished and Diminished.

Half-Diminished = 1 b3 b5 b7
Diminshed       = 1 b3 b5 bb7 (the 7 is flat twice thus making it a 6)

This might be confusing at first.  But once you “do the math”, you’ll see quickly that there isn’t much to remember.  Also, (in my experience) these chords are not very common (and for that reason, I’m not too familiar with them  :-).  But I love using them because they add such wonderful, (usually) unexpected texture.  Hopefully the progressions below will give you a flavor.

In my search for other material on these chords on the web, it seems like “diminished” is often also referred to as “diminished 7” (“dim7”).  But I was not able to find a slick way of pointing to the half-diminished chord except for “min7 b5”.

For the purpose of this post, I’ll be using “dim7” and “min7 b5”.

First, let’s look at the shapes.  Here are 2 ways of holding each.  For each of these, make a note of where the root note is (hint: either the A or D-string).

As mentioned above, the diminished 7th chord starts at the root and has a minor 3rd, a flat 5th, and a flat-flat 7th.  Interestingly, this puts each note in a perfect repeatable pattern.   For instance:
Eb (major) = Eb(1) G (3)  Bb(5)

Eb dim7    = Eb(1) Gb(b3) A (b5) C (bb7)

What if we started with Gb?

Gb (major) = Gb(1) Bb(3)  Db(5)
Gb dim7    = Gb(1) A (b3) C (b5) Eb(bb7)

Notice that Gb dim7 has the same notes as Eb dim7!  How about for A?

A (major)  = A (1) C#(3)  E (5)
A dim7     = A (1) C (b3) Eb(b5) Gb(bb7)

You can image that you’ll get the same notes again if you start the pattern using C.

Since there are only 12 notes (C C# D D# E F G G# A A# B) and this chord uses 4, there can only be 3 different diminished 7th chords!

Now, let’s try using these in progressions along with other chords that we’ve already looked at in past posts.

Diminished 7th Example 1
|C     |D     |Bm      |Em     |  (repeat)

|C     |D     |Eb dim7 |Em     |  (repeat)
This  progression is in the key of G which would have a Bm as the 3-chord.  (see previous post)
For hearing the full effect of the dim7 chord, try playing the 1st line (maybe repeat a few times) then try the 2nd line (and repeat a few times).  You’ll notice that the Eb dim7 replaces the Bm.  And you might hear how the Eb dim7 provides more “energy” and “tension” to be “resolved” by the Em chord.
Diminished 7th Example 2
|Dm7     |G7     |Cmaj7      |Db dim7  |  (repeat)

This example in the key of C is a more jazzy example (or funky a la Sunday Morning by Maroon 5??).  Again, the dim7 chord provides a tension to be resolved by the following chord (Dm7 in this case).  And you can hear a moving bass line from: C > Db > D.
Half-Diminished Example
|Bm b5   |E7     |Am       |Fmaj7     |  (repeat)

This example might be a bit more classical or Spanish (in fact, try strumming Flamingo style… perhaps more on this later).  This would be considered to be in the key of C.  The Bm b5 chord is the “natural” chord create from the 7-note in the scale.  While the E7 is “out of scale” (E is the 3rd note so it would have been Em using the notes from the C major scale).  The Bm b5 chord “wants to go to” the E7 which “wants to go to” Am.
Hopefully you now have an idea of how diminished chords can be used to create tension and unrest and that you found these examples useful!