5. How to build chords

A chord is a set of notes played together. And the name of this chord depends on the root note, and on how many notes there are in it and the intervals that separate each note.


Triads are chords made of 3 notes. They are at the basis of all chords.

To build them we need a root note - which will give the chord its name - a third and a fifth.

So if I want to make a chord of C
I take a C, the third E and the fifth G.
That makes a C major chord


Because between C and E there are 2 tone, which is an interval of major third.
And between the C and the G there is a interval of 3,5 tones, which is an interval of a perfect fifth.
So a root note + a major third + a perfect fifth makes a major chord. Which is considered to be a happy chord. It sounds happy.

To make it a minor chord, I have to lower the third by a semi-tone. So it becomes Eb.
And the interval between the root note C and Eb is 1,5 tone, which is an interval of a minor third. The interval between C and G is still a perfect fifth.


So a root note + a minor third + perfect fifth make a minor chord. That's considered to be a sad chord, it sounds kind of sad.

The only difference between a major chord and a minor chord is the third. This note alone will determine the state of the whole chord.

And you can actually change the order of the notes, the voicing, it will still stay the same chord.

For example if I write my C major chord E G C it can be described as a E chord with a third and a sixth, but it is still a C major chord. We call that an inversion.


If I remove it the third in my chord, the chord is neither minor or major, this what we call a power chord. This is just a root note and a fifth. It's used a lot by guitarists.

So I can alter the third to make the chord major or minor, but I can also alter the fifth.
If I move my perfect fifth up by a semi tone, it becomes augmented. And if I move it down a semi tone, it becomes diminished.

So a chord with a major third + a augmented fifth is called an augmented chord. Such as C E G#, that's a C augmented chord. It's considered to be more of a bright chord.

The other way around, a chord with a minor third + a diminished fifth is called a diminished chord. Such as C Eb Gb. It's considered to be a dark chord.


And that's pretty much all the most used Triads.  Major, minor, augmented and diminished.
We could create a triad with a major third and a diminished fifth, which I heard was called hard - diminished, which sounds harsh, but to it's not really used.


In fact if we see these 3 notes together, C E and Gb, it's often as being part of another chord (other than C), often with a forth note added.
So this hard-diminished chord with a major third and a diminished fifth is not really used as is.

In fact, every chord can be considered as a superposition of thirds:
- A major chord is a major third + minor third.
- A minor chord is a minor third + a major third
- A augmented chord is 2 major thirds stacked up
- And a diminished chord is 2 minor thirds stacked up


Maybe that explains a bit better why we don't really use a major third with a diminished fifth, as then, there wouldn't be an interval of third between the third and the fifth of our chord.

So when you're using a scale, you can build chords by stacking up thirds.

In practice, that means that when you're using a scale, you can build chords by taking one note every two, starting with your root note. The space between each note will then define the nature of the chord.

In the scale of C major for instance, (that's all the white keys on a keyboard) if I build a C chord, I start from C, leave a note, then take a note, that's E, leave a note, take a note, that's G.