Basic Chord Theory


Here is a guide where you will learn the basics of chord theory; what harmony is and how musical chords are built.

What is a Chord?

What is a Chord? Let us start by clearing up what a chord is and what a good definition of music chords is.

The word Chord itself is derived from the ancient Greek word “khorde”, which meant "gut, string of a musical instrument".

The word for chord in Modern Greek is “Synchordia” which means “strings sounding simultaneously”.

Here is a short and simple chord definition:

A chord consists of three or more notes played together.

But the notes of a chord can actually be played in many different ways and sometimes not together at all!

Chords can be played blocked (all notes simultaneously) and broken or “arpeggiated” (one after the other, like plucking a chord on a guitar).

When studying music and chord theory, you will learn that chords can sound peaceful, or weird, ugly or nice, spicy or sweet.

Chords can sound as if they need desperately to go somewhere… and the next chord can either sound like “home” or keeps the tension going.

You can use chords in a progression to lead the music forward, or coming to a stop. When learning about chord theory you will see that chords are very powerful ingredients in music indeed!

Chord Theory: Harmony

Chord theory includes the study of Harmony. Basically, any two notes sounded together is creating what is called harmony. The harmony can be either consonant (harmonious) or dissonant (not harmonious).

So what is Harmony? Harmony happens (!) when notes in general are played simultaneously. Harmony can be created by:

  • Intervals (two notes played together).
  • Chords(three or more notes played together)
  • 2 or more melodies played/sung together, for example the well known round “Row, row, row your boat” starting at different times (a simple form of polyphony is created.)

3 Note Chords, or Triads

The basic form of a chord is made up of three notes, stacked on top of each other an interval of a third apart. These thirds can be either big (called major) or small (called minor).

What is a third? To understand chord theory, you need to know a little about intervals, especially thirds since this is what the chords are made up from!

On a piano keyboard you can easily see what a third is:

The interval (distance between the notes) of a third is either two whole steps (major third) or one and a half step (minor third).

Triads are made up of two thirds; one major and one minor. See how the three notes are all on lines (or in the spaces) evenly spaced a third apart:

The bottom (lowest) note is called the root and gives the name to the chord; the next note (middle) a third higher is called…the third!

This third has an important job, since it decides whether the chord is a major chord (a major or big third from the root note) or a minor chord (a minor or small third from the root note).

The last note one third up from the middle note is called the fifth- because the notes are counted up from the root.

The basic triad is named after its root, and if the first third is major or minor. In this case the root is a C, and the first third is a major third. So the chord is called C major, but written only “C”. If it was minor it would be written “Cm”.

4 Note Chords, or Seventh Chords

If you add one more third on top of a triad in root position, you have a four note chord, also called a seventh chord.

When the stacked thirds are (from the note C as being the “root”) major, minor, major, the chord is a major 7th chord, written: Cmaj7 .

If you have major, minor, minor thirds, it becomes a regular 7th chord, written: C7.

“Bigger” or Extended Chords

Keep on stacking thirds like “Lego pieces” on top of the triad; the next third is the 9th, then the 11th and finally the 13th.

Here is a Ninth Chord (C9) starting on C:

Here is the interval of an eleventh (a), and an Eleventh Chord (C11) (b):

And finally, adding one last note, is the Major Thirteenth Chord (Cmajor13) The first example here:

Why not more?

Well, with a 13th chord you are actually using all of the 7 different notes of that scale- adding more would just repeat notes.

The notes that are added to the basic triad are written as numbers: 7, 9, 11 or 13 to the right of the chord name, like this: C7, for example.

C is the basic triad, in this case a major chord, and added on top is a seventh (counting up from the root up).

C9 includes all the notes, root, 3rd, 5th, 7th, and 9th, but only the root (C) and the last (9) is written. This works in the same way with the 11 and 13 chords.

Too many notes? Use Added Tone Chords!

C13 has an awful lot of notes… 7 of them!

So instead you will often see the chord formula C major 7 (add13), which includes the basic triad plus the 7th and the 13th. This note is the same as the 6th as well, which makes it a bit easier to play!

Now, all the chords on this page were in root position, where the root is the bottom note.

But all chords can be inverted, or rearranged, to better fit together and be easier to play smoothly.

As long as you keep the same chord notes, you can reorganize them anyway you like.