All Types of 7th Chords Are a Combination of Major & Minor 3rds

How to form all types of 7th Chords with a stack of 3rds.

Click on this link to watch this video on YouTube: https://www.youtube.com/watch?v=oYoe545rZLs&feature=youtu.be

Good morning. This is Duane and we’ve been doing a series called Good Stuff You Really Ought To Know About Music. One thing you really ought to know about music is how thirds combine, how intervals of thirds combine to form seventh chords. Yesterday, we took up the way that major and minor intervals combine to make triads. If you remember, we define a major third as two whole steps. Whole step, whole step, so that’s a major third. We define as a minor interval, two notes that are a half step less than a major interval, in other words, one, two, three, three half steps instead of four.

A major interval has four half-steps, one, two, three, four. While a minor third has three, one, two, three. We’ve said that to form a major chord, you have a major third on the bottom and a minor third on top. If we have a minor chord, then we have a minor third on the bottom and a major third on top. Both of those are balanced, aren’t they? In other words, they have one major third and one minor third or one minor third and one major third. They’re balanced, right? That’s why they’re used so much.

If you have an unbalanced chord, it creates a lot of tension. A lot of tension, for example if I take a major third and put a major third on top of it, that’s a nice chord but it creates tension. It wants to be resolved somehow, doesn’t it? You don’t want to really walk away from that chord and go to bed with that on your mind. Same way with if you’d stack two minor thirds together. IF you have a minor third with another minor third, that creates a lot of tension. That creates our basic four kinds of chords, doesn’t it? Major chord, minor chord, diminished chord and augmented chord, but only the major and minor chords are well-balanced in that they have a minor third and a major third in them.

Now we’re going to take up seventh chords. Today, you know what a seventh chord is, a seventh note of the scale, right? Or the flat seventh note of the scale. If we have a major triad and we add a minor third on top, that’s called a seventh or technically it’s called a dominant seventh. That chord wants to resolve to F, C seventh, one stroke, resolved. It doesn’t always have to, but it usually does. If you have a major third, a minor third and another minor third, that’s a dominant seventh and it wants to go some place.

If on the other hand, you have a minor third with a major third and a minor third, see that’s well balanced, isn’t it? Because you have a minor third on the bottom, major third in the middle, minor third on top. That creates a mellow sound so that’s called a minor seventh chord. That’s a C minor seventh chord. If you have a minor interval, a minor third and a major third and then another major third, that creates a lot of tension too, doesn’t it? Because it’s unbalanced, it’s got two major thirds in it and only one minor third. The balanced intervals are more, I’ll call them stable than the unbalanced intervals.

Now we can also have a diminished, a minor third and a minor third if we take another minor third, we’d have to double flat that B, wouldn’t we? What we’d end up with is a diminished seventh chord. I know it looks like a sixth but in music theory, you’d have to call it a diminished seventh chord. Look what that is? It’s a minor third with a minor third with a minor third and a minor third. It’s all minor thirds, isn’t it? It’s very unbalanced and that’s why it creates that. You often hear that in movies or TV shows when they’re building up tension. You’ll hear diminished seventh chords.

Let’s see. I guess that’s it. You could have a major third, a major third and a minor third and that’s a very little-used chord but it’s possible, that’s a C augmented major seventh. C-major seventh with a raised fifth, equivalent to the augmented chord. That’s how major and minor thirds are combined to form sevenths. Tomorrow, we’ll take up another subject and hope to see you there. If you’re not already signed up for our free newsletter, free series of videos, come on over to playpiano.com and sign up for them. Hope to see you there. Bye bye for now.

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Here’s a great little book on chords and chord progressions on Amazon: http://www.amazon.com/Piano-Chords-Chord-Progressions-Exciting-ebook/dp/B0076OUGDE/ref=sr_1_1?s=books&ie=UTF8&qid=1404158669&sr=1-1&keywords=piano+chords+duane+shinn

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