Basic Piano Chords – Theory – Diatonic Sequence

This post on basic piano chords for the C major scale will give you a solid foundation for the basic chords in all scales. Once this theory is known, it can be applied to all major scales, and it will give you an insight on how chords are built and how chords are named.

Once you are done with this, you will be able to dissect chords with strange names like B minor 7 flat 5. You will know why they are named that way and you will be able to tell which notes it contains.

If you already know the basics, but you are looking for more information on inversions and smooth transitioning between chords then please check out my blog post ► Chord Inversions to Transition Chords Smoothly.

Oh and if you were looking for chord formulas instead; I have them right here for you.
► Chord Formulas

Before I can teach you about the basic piano chords there are a few prerequisites.

1. the major scale
2. halftones and whole tones
3. some basic intervals

Prerequisites

The Major Scale, Semitones and Whole Tones

To make the most of what follows it is best that you are familiar with semitones (or halftones) and whole tones, as well as some basic knowledge on the Major Scale.

Get familiar with semitones, whole tones and the major scale.
► Piano Scales: The Major Scale

Some Basic Intervals: Minor and Major Thirds

Without some basic understanding of minor and major thirds, what comes after will be hard to understand so I will elaborate on the subject here. This section will become an in-depth post soon, but for now, here is what you need to know.

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If you don’t know what intervals are in musical theory, keep an eye out for a future post where I explain this in-depth.

An interval is represented by the distance between two note names and their distance in tonality.

The most important interval that we use, to build up our basic chords, is the third.

The third, like most intervals, comes in two flavours:

• minor third
• major third

In the image above, when we travel from the C to the E, we are passing C as 1, D as 2 and E as 3.
The distance from C to E by note name is three, which we call a third interval.

We can do the same when we travel from D to F, we are passing D as 1, E as 2 and F as 3.
the distance from D to F by note name is also three, which is also called a third interval.

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There is however a difference in tonal distance for those two examples:

• from C to D is a whole tone and from D to E is also a whole tone. That means there are two whole tones between C and E. In this case we speak of a major third.
• from D to E is a whole tone and from E to F we have only a halftone. That means there are one and a half tones between D and F. In that case we speak of a minor third.

minor third: one and a half tone interval
major third: two tone interval

Putting it all together

The basic piano chords, and not just for piano but for any instrument really are a stack of third intervals. We distinguish two types of basic chords: triads and tetrads. The difference between those two is fairly simple; a triad chord has three notes and a tetrad chord has four notes.

To find those notes for both types of chords, we simply stack third-intervals on top of each other. We will make this crystal clear in the next few sections.

First Stack of Thirds

Let’s look at the C major scale again, but with where each note has a third interval stacked on top like this:

By counting the number of tones between each of those notes, we can deduce which are minor and which are major thirds. Major thirds are showing as +3 and minor thirds are shown as -3 in the image.

This first stack of thirds determines the nature (minor or major) of the chord.

Second Stack of Thirds

The same C major scale, where each note has two third intervals stacked on top like this:

Ok, this is starting to look like chords now! This gang of chords are the TRIADS of the C major scale. The word triad means a group of three notes. (not to be confused with the Chinese organized crime)

You can see that each of those chords is a combination of a major third and a minor third except for one: stacked on top of the B are two minor thirds.

The Perfect Fifth and the Tritonus

If you calculate the tone distance from the bottom note to the top note of each of these triads you get three-and-a-half tones. (2 whole tones for +3 and 1 whole tone and a half for -3)

Perfect Fifth: a distance of three-and-a-half tones.

As you can tell, a perfect fifth is very common. Almost every chord in the C major scale has one. I will disclose to you that the same is true for every major scale, not just for C.

In C major, the exception to this perfect fifth is on the seventh note: B

The distance from B to F is exactly 3 whole tones which is half a tone less than a perfect fifth. For this reason this interval is called a flat fifth. However, this interval has another name that is very apt: the TRITONUS or TRITONE.

Flat Fifth or Tritone: a distance of three tones.

The tritone is an interval that sounds with a lot of tension. When used in music it is an interval that needs a resolution. For now, that is all you need to know, I will make you understand exactly what that means in a future video because that will make so much more sense.

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Naming the Triads

We are ready to name our triads. It is so easy now:

Remember the first third of our stack of thirds determines the nature of the chord. The perfect fifth is so common in a chord that it only has an effect on the name of the chord if it is not perfect.

So when we apply that logic we can name our triads as follows:

There is a pattern here that you can remember which applies to any major scale starting from the root of the scale going up: maj – min – min – maj – maj – min – min flat 5 – maj

Third Stack of Thirds

With the risk of sounding like a broken record, here is the same C major scale, where each note has three third intervals stacked on top like this:

These chords are the TETRADS of the C major scale. The word tetrad means a group of 4 notes.

All of those chords have something in common; they either consist of two major thirds and one minor third or the other way around, two minor thirds and one major third.

The Minor and the Major Seventh

When we count the note distance between the bottom and the top note of each tetrad we always get seven. The interval is therefore called a seventh.

However, when we calculate the tonal distance between the bottom and the top note of each tetrad we get either five whole tones or five whole tones and a half tone.

The latter determines the nature of the interval:

minor seventh: five tone interval
major seventh: five and a half tone interval

Naming the Tetrads

To name the tetrads, we have to take into account another norm:

If the triad is major, the tetrad normally has a major seventh.
If the triad is minor, the tetrad normally has a minor seventh.

You may remember that rule with the perfect fifth that says the fifth only has an effect on the name of the chord if it deviates from the norm? Well, guess what, the same applies for the seventh interval.

And as it so happens, in all the tetrads of the C major scale there is only one exception: the G or the fifth chord of C major. The triad is a major chord but the tetrad has a minor seventh!

Now we do need to show in the name of the chord that we want a tetrad versus a triad so our triad names all get a notation with an added 7 like this:

You can see in the image above that we dropped the maj part in the G chord. This is the exception: while we do have a major third as the first interval, we also have a minor seventh. You could say that this makes the chord neither major nor minor. Hence we drop the keyword.

You will often hear musicians call this a G dominant.

One more thing to note is that this G7 tetrad has a B and an F note. The other chord that has those notes is the Bmin b5 chord. You may remember that this is the famous TRITONUS interval that causes so much tension and demands a resolution.

Applying This to any Major Scale

Quick take-a-way: To apply this to all major scales you just need to remember this sequence:

In this sequence, you can substitute the Roman Numerals with the notes of your major scale. So for instance in the key of G major that would become:

And you are good to go!!!

Say What?

My goodness! What a journey we made! We learned so much in this post that we risk getting overwhelmed!

I hope this post will help you to understand how chords are formed and how they are named, with this information you have about 80% of all chord-theory you’ll ever need.

We will still learn about adding tension and playing inversions… Not to mention the circle of fifths… But enough for now before our heads explode!

So do I have to remember all that theory while I am playing?
So lucky that I can say NO to that question!

As with many things, it is good to know the theory, so you get answers to questions that otherwise get left unanswered. This theory will help you as you figure out how to play chords on your instrument but gradually your muscle memory will take over and the brain processing will stop.

In future posts, I will add lots of exercises that will get your muscles remembering the motions at the speed of light!

Happy playing!

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