LadyDpiano: Play Diminished 7th, Half Diminished 7th Chords

half-diminished seventh chord on C (Photo credit: Wikipedia)

Diminished 7th chords are very unique and interesting. As you learned earlier, the word diminished means "made smaller." When a perfect or major interval is made smaller by a half step, it becomes a Diminished Interval. The Diminished triad is a Minor triad with the 5th tone made smaller by one half step. If you missed my earlier post, you can see it here.

They are the only type of chord that is a stack of minor 3rds. If you count from one chord note to the next, you will find that they are all equidistant.

There are only three groups of diminished 7th chords:

1. C-Eb-Gb-Bbb

2. C#-E-G-Bb

3. D-F-Ab-Cb

That's right... these chords all share the same notes.

Abdim7
Bb dim7
Cb dim7
D dim7
F dim7
G# dim7

Here's what I've learned from Duane Shinn

Diminished 7th chords can be used as "modulation agents", "transposition agents", and "transition agents". They can transform themselves into 7th chords by just moving any one note. They can also be changed into 6th chords and major 7th chords with a minimum of movement.

Half-Diminshed 7th Chords

In this chord one of the intervals is a major third instead of a minor third.

These chords are very important. Here's what I learned from Jermaine Griggs:

Not only do they naturally occur on the 7th tone of any major scale, they are used as great preparers for dominant chords on the 5th tone.

If you play gospel, you’ve undoubtedly used a half-diminished 7th chord on the 2nd tone of the scale to lead to the 5th.

By going to the 7th tone of any scale and playing every other note, you’ll form the half-diminished 7th chord. For example, in C major, the 7th tone is B. Simply play B + D + F + A and you’ve got yourself a B half-diminished 7th chord.

The first three notes of a half-diminished 7th chord in root position look identical to the diminished triad. In the chord, B half-diminished 7th, if you take off the last note, you’re left with B + D + F, which is a B diminished triad.

And diminished chords are formed by simply stacking a bunch of minor third intervals together.

Note: Minor thirds have three half steps between them.

B to D is minor third.
D to F is minor third.

Where the “half-diminished 7th” chord differs is in the last interval. Instead of another minor third like the B diminished 7th chord (B + D + F + Ab), you play a major third, which is four half steps.

F to Ab is minor third.

F to A is major third. <---- This is the one you choose the differentiate the half-diminished 7th from a typical diminished 7th chord.

Compare the two: Half-diminished 7th vs diminished 7th

B diminished 7th = B D F Ab

B half-diminshed 7th = B D F A

It’s all in the last interval… and the difference in a half step.

A huge investment to your piano playing is purchasing the Secrets to Playing By Ear book. It's about piano techniques, principles and tips that will enhance your ability to recognize songs, melodies and chords by ear!

Once again, it's been a pleasure teaching you and I look forward to helping you for years to come.

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Warmly,