Chordal Theory: Triads and Extended Chords

In this lesson, we are going to take an in-depth look at chords. Since this is a theory lesson, it will apply to all musicians, regardless of the instrument they play. Even drummers should learn a little bit of music theory.

By the end of the lesson, not only will you have a solid understanding of triads, but you’ll be working through extended chords as well.

Major Scale

You cannot begin to understand music theory if you do not have a solid grasp of the major scale. You need to know how it’s constructed, and more importantly, how it works.

The major scale follows a formula of:
Tone – Tone – Semitone – Tone – Tone – Tone – Semitone

This formula indicated the interval between notes. So, start on any of the chromatic notes. To keep the lesson easy, we’ll start on G. A tone up from G gives us A. Move another tone and we’ll get B. A semitone from there gives us C. Then the three tones in a row give us D, E, and F# respectively. And we’ll end with a semitone to G again.

G (+t) A (+t) B (+st) C (+t) D (+t) E (+t) F# (+t) G

Triads

Triads are chords. A chord is defined as three or more different notes played at the same time. Most musicians can play a few chords, but very few know the theory of those chords. It’s essential to understand chordal theory so that when you write a song or solo, you can be more expressive and play to the mood of a song better.

There are four primary triads that we use in music.
They are:

  • Major
  • Minor
  • Augmented
  • Diminished

I will use the G major scale to demonstrate the triads, but any other major scale will work equally well.

G         A         B         C         D       E         F#         G
I           II         III        IV        V       VI       VII         I(VIII)

We use roman numerals under each note to illustrate the degree of the scale. So G is the first degree, and D is the fifth degree and so on.( Classically trained musicians refer to the degrees differently.*)

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Formulas:

Major:
To form the major triad, we use the first, third and fifth degree of the scale. So G major is:
G B D
I III V

Minor:
To form the minor triad, we use the first, flattened third and fifth degree of the scale. So G minor is:
G Bb D
I IIIb V

Augmented:
To form the augmented triad, we use the first, third and sharpened fifth degree of the scale. So G augmented is:
G B D#
I III V#

Diminished:
To form the diminished triad, we use the first, flattened third and flattened fifth degree of the scale. So G major is:
G Bb Db
I IIIb Vb

Now you should work out the four triads listed in every key.

Extended Chords

If all you know are the triads, you will struggle to express yourself as fully as possible. As you progress musically, it becomes vitally important that you understand music theory on a deeper level.

Sure, music theory can be hard to understand and isn’t always intuitive. But, with a chord construction knowledge, you will be able to elevate your songwriting to the next level.

7th Chords

To be able to identify chords, you must be able to name them correctly. This will help your bandmates understand what you are talking about.

After all, without us calling things by the same name we’d all be lost.
Whenever we talk about a triad, if we don’t say “major”, it is implied. So when we’re asked to play C, it is assumed that we mean C Major.

However, when we start using 7th chords, we can no longer assume that to be the case. A C7, for example, is, in fact, a C Dominant 7.

The most common types of 7th chords are the major, minor and dominant 7. Although these are by no means the only types of 7th chords, they are the only one we will deal with in this lesson.

Extended Chords

Extended chords are chords that contain a ninth, eleventh, or thirteenth. These are considered the extended notes. It is important to note that these can often have two names.

The ninth is also the second, the fourth is also the eleventh, and the sixth is also the thirteenth.

Formulas for 7th Chords and Extended Chords

So now you know the basics of what makes these chords, but let’s look at some of the formulas involved with building these chords.

Dominant 7
I-III-V-bVII

Major 7
I – III – V – VII

Minor 7
I – bIII – V – b7

Second/Ninth
I – II – III – V
I – III – V- IX

Fourth/Eleventh
I – III – IV – V
I – III – V – XI

Sixth/Thirteenth
I – III – V – VI
I – III – V – XIII

So, in the key of G, the chords will be built as follows:

Dominant 7
G – B – D – F

Major 7
G – B – D – F#

Minor 7
G – Bb – D – F

Second/Ninth
G – A – B – D

Fourth/Eleventh
G – B – C – D

Sixth/Thirteenth
G – B – D – E

*The classical notations for degrees:

I           Tonic
II          Supertonic
III        Mediant
IV        Subdominant
V         Dominant
VI       Submediant
VII     Leading note or Subtonic

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