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Chords Part 4: Diminished and Augmented Triads

So far in this series, we’ve looked at major, minor, major seventh, minor seventh and dominant seventh chords. Today, we’ll take a look at diminished and augmented chords. Note: if you have not read the previous postings on this topic, take a look at them before reading on.

As we saw in part one of this series, major triads are created by taking some root, for example C, then adding a major third, and a perfect 5th above (in this case giving us C-E-G). To create a minor triad, we do the same, except instead of moving a major third above the root, we take a minor third and the perfect fifth (so a C minor triad would consist of C-Eb-G).

Diminished Triads

To create a diminished triad, we begin by taking some root (let’s stick with C), and then we add a minor third above, plus a flat 5th on top. To find the “flat 5” we move our perfect 5th back one half step, giving us C-Eb-Gb.

Another way of thinking about diminished triads is to think of them simply as stacked minor 3rd intervals. The minor third consists of one whole step plus one half step. If we move from C up a whole step then a half step, we land on Eb, and then if we again move up a whole step then a half step from that Eb, we will land on Gb.

To turn this diminished triad into a diminished seventh chord, we simply add one more minor third on top of the Gb, giving us C-Eb-Gb-A. Technically speaking, we should name that final note Bbb, or “B double flat,” because that last note, the 7th, should get its name from the 7th note in some scale starting on C. If we count up our musical alphabet from C, we should have some kind of the following notes: C-D-E-F-G-A-B, and by some kind I mean that these notes can be sharpened or flattened as needed. However, it is simpler to think of this diminished seventh as A instead of Bbb for practical purposes. These notes are called enharmonic equivalents, a topic for another posting.

Augmented Triads

To create an augmented triad, we effectively stretch out the perfect 5th in a major triad to give us an augmented or sharp 5th. To do this, we move our perfect 5th up one extra half step; so, if we again look at this triad starting on C, we will end up with (C-E-G#—as opposed to C-E-G in our major triad).

Another way of thinking about these triads is to consider them as a series of stacked major thirds. The interval of the major third consists of two whole steps, so if we move up two whole steps from C, we will land on E, and then if we move up two whole steps again from E we will finally land on G#.

These triads are fun to experiment with because of their symmetry—diminished triads are stacks of minor thirds and augmented triads are stacks of major thirds. Take some time to create some of these on your own. Hint: they are easiest to picture as either “squished” minor triads or “stretched” major triads. That’s all for now, but we’ll be sure to look at where these triads tend to appear in music in a subsequent posting.