Q & A: Diminished and Half-Diminished Chords

From a recent email:

Hi David,

I have played guitar for forty-two years. My life evolved around major, minor, 7th and 9th chords. I am now learning to read and understand theory and dabbling in some jazz stuff. I seem to be doing alright however I am having trouble with diminished vs. diminished 7 vs. half diminished and so on. After speaking with a few others if seems that I am not the only one confused about the differences. Your fantastic lesson on diminished and augmented chords helped vastly however I was hoping you were going to touch on the “other” versions. My question is – is there a chance that maybe you could write a short lesson on this subject?

Thanks

Hello and thanks for writing.

Hopefully, we may be able to cut through your confusion without resorting to an entire article. Let’s start with the diminished chord. As with all four of the very basic types of chords (major, minor, augmented and diminished), the dimished chord is built on the triad of root-third-fifth. However, both the third and the fifth have been lowered a half-step from what they would be if they were part of a major chord.

Major Chord: Root  3rd  5th

Diminished Chord: Root flat 3rd  flat 5th

In jazz music, the term “full diminished” refers to the diminished seventh chord. To create a diminished seventh chord, you start with the diminished triad and then add the dominant seventh after it, too, has been lowered a half step. In other words, it’s the “flat flat seventh,” which is the same as the sixth position of the major scale.

A “half diminished” chord is a diminished chord (root, flat third, flat fifth) to which the normal dominant seventh (that’s the flat seventh) has been added. Typically this chord will be labeled as “m7b5” on a chord sheet.

Using the key of C as an example, here are your chords in question:

C Major – C  E  G

C Diminished – C Eb Gb

C Diminished 7 – C Eb Gb A (A being “Bbb” if you will)

Cm7b5 (or half diminshed) – C Eb Gb Bb

I hope this helps clear things up. Please feel free to write again if you need further (or better!) explanation. I look forward to chatting with you again soon.

Peace