Guitar Chord Theory – The Complete Guide to Understanding Chords

Interested in learning about guitar chord theory? Our introductory guide explains (in very simple terms) what chords are, how to read chord charts, how chords are named and how chords are constructed. So if you have ever wanted to understand chord theory rather than simply memorising individual chord shapes this guide is for you.

What are chords?

A chord is a combination of three or more different notes played at the same time, usually to support a melody.

This doesn’t mean playing any combination of three or more notes on the guitar will sound musical. But, technically, provided you are playing a combination of three or more notes at the same time, you are playing a chord.

What are Arpeggios?

An arpeggio is simply a chord with the notes played sequentially e.g. one at a time, rather than at the same time, as in when strummed.

Types of Chords: Triads, Sevenths and Extended Chords

Chords can be categorised based on the number of notes they are constructed from and include triads, seventh chords and extended chords.

Triads

Triads are chords that consist of three notes, the root note, third and fifth.

What are thirds and fifths?
Thirds and fifths are just two types of musical intervals. Intervals refer to the ‘musical distance’ between two notes e.g. how many notes are located between two notes.

We’ll explain intervals in far greater detail as we go along as intervals are essential to music theory, but for now keep in mind intervals are used to reference the relationships between notes and are useful when constructing chords and scales.



There are four types, or qualities of triad chords. These are known as major, minor, augmented and diminished and are the among the most common chords played on guitar.

Seventh Chords

Seventh chords are simply triads that include the seventh interval from the root note of the chord. Again, if this doesn’t make a lot of sense right now, don’t despair, this will become much clearer as we go along.

Extended Chords

Extended chords are constructed from more than three notes, with any additional notes beyond the basic triad extending beyond the 7th musical interval. This means they include notes from an octave higher and include 9th, 11th and 13th chords. An octave, if unaware simply means a note of the same pitch but at a higher frequency. For instance your open E string is technically the same note as the 12th fret of your E string but of a higher frequency.

What about two note chords?
You may have heard guitarists refer to two note ‘power chords’. Power chords are simplified versions of chords that include the root note and the fifth interval. They are neither major or minor in quality as they do not contain a third which distinguishes whether a chord is major or minor in quality.

For now it is helpful to understand, two notes played together is harmony (the combination of one or more notes played at the same time) but isn’t technically a chord. However, you may see two note power chords referred to as ‘partial chords’.

Open and closed position chords

Most beginner guitarists will start out by learning open position chords. Open position chords include open strings (unfretted strings) and are played in the first three or four frets.

Closed position chords (also known as barre chords) do not contain open strings and require the strings to be ‘barred’ across one fret (please see image below), replicating the nut, and preventing any open strings from ringing out.

bare chord

Barre chords can be played anywhere on the neck of the guitar. Typically guitarists tend to learn these once they have mastered open position chords as open position chord shapes are incorporated in barre chords, along with barring the entire fret closest to the nut using the index finger.

Chord Voicings

Open and closed position chords are just two examples of different chord voicings e.g. playing the same chord utilising different positions on the guitar neck.

Keep in mind chords are constructed from notes and when you consider there are only 12 notes in the chromatic scale (the chromatic scale includes all 12 notes in western music) and most guitars have at least 114 frets (21 frets X 6 strings) it becomes apparent that there are many different ways to play chords on the guitar.

How to Read Chord Charts

Chord charts demonstrate how chords are intended to be played.

The following is a chord chart showing an ‘A major’ chord in open position:

A major

The chart itself is essentially an image of the guitar fretboard. The bass strings (heavier gauge strings) are on the left and treble strings on the right. (* some chord charts may be presented in a horizontal layout)



If you are a right handed guitarist, this represents the guitar fretboard if you were looking at it directly.

  • The vertical lines represent the strings of the guitar.
    In the chart above the bass strings are shown slightly thicker than the treble strings, this is not always the case and can vary from chord chart to chord chart.
  • The horizontal lines represent the fretwires.
  • The thicker black line shown at the top of the chart indicates the nut.
  • The black dots represents the finger placement on the fretboard.
    The root note is sometimes shown as a white dot with black outline but as in the chart above, not in all cases.
  • The ‘X’ above the first fret indicates the string is not to be played.
  • The ‘O’ indicates the string is to be played but is unfretted, or in other words it is an open string.
  • Lastly, the numbers at the bottom of the chart represent the fingers used to fret the notes.
    In this case the first (index finger), second (middle finger) and third finger (ring finger) are used to play the A major chord. Some chord charts include numbers representing finger positioning, some do not.

Chord Fingering

 

Chord charts are not just used to represent open chords. Below is an example of a A barre chord.

A Major Barre Chord

Being a closed position chord, the 5th fret is barred which is indicated by the curved line above the fifth fret, you will also notice the absence of the thicker black line representing the nut. You will also notice the number 1 used on the notes played at the fifth fret. This means all the notes that align with the fret are fretted using the first (index finger).

Technically only the frets that are numbered are required to be played but it is much easier to simply barre the entire width of the neck.

Unlike an open position chord, the chart itself is a representation of a section of the fretboard taken from the 5th fret, indicated by the ‘5th’ marked on the left side of the chart.

How Chords are Named

Chords are named based on the root note of the chord and the quality of chord. For instance a D major chord takes its name from the root note of the chord which is ‘D’ and the chord being a ‘major’ chord.

 When discussing major, minor, augmented etc. we are referring to the chord’s quality, however these are often referred to as chord types, which are not to be mistaken for triads and extended chord types. 

Root Notes

The root note of a chord, corresponds with the letter given to the chord name. It helps to think of the root note as the foundation that the chord is built upon.

For example D is the root note of all D chords (e.g. major, minor, augmented, suspended etc.). C is the root note of all C chord types and so on.

In the majority of cases (but not always) the root note is the first and lowest pitched note in the chord. Chords that consist of the root note being the lowest pitched note are called ‘root position chords’.

For instance, when playing an open position D chord, the lowest note played is the open D (4th string) as the A and low E strings are not played.

D major

In the majority of open position chords the root note will be a note played on one of the bass strings either the low E, A, or D strings.

Another example of this is the open A major chord. The first string played, is the open A string which happens to be the root note. The low E string is not played.

Repeat Notes

Many chords include more than one root note. For example the E major chord consists of both the open low E and high E string being played as individual notes of the E chord.

E major

It’s not just the root note that can be repeated. All notes used to construct the chord can be repeated. For instance, the following are both C major chords.

C major is constructed from C (root note), E and G.

C major chord voicings

While the first chord shape contains just the three notes including the open string ‘D’, the second example utilises 5 notes, however the C, and G are repeated.

Chords shapes that utilise repeat notes often do so to make the chord shape easier to play (consider the difficulty of muting the first, 5th and 6th strings in the first example) and tend to sound more expansive, and fuller.

Chord Qualities

Regardless of your experience with music, you have likely heard the musical terms ‘major’ and ‘minor’.

‘Major’ or ‘minor’ is a way of describing the chords ‘quality’ and relates to its own distinctive sound, or flavor.

For example, major chords are often described as sounding happy, while minor chords are often described as sad or serious. The musical intervals that make up the chord define the quality of the chord. More on this shortly.

Chords are not restricted to only major and minor however. The table below shows a list of the four most common qualities of chords and their naming conventions.

Chord Quality Suffix Description
Major No suffix used Happy, simple, resolved
Minor min Dark, serious
Diminished dim Tense, dissonant
Augmented aug Suspenseful, unnatural

Other less common chords include:

Chord Quality Suffix
Suspended fourth sus4, (sus)
Added ninth add9
Minor added ninth m(add9)
Fifth 5, (no3)
Sixth 6
Minor sixth M6m (-6)
Sixth, added ninth 6/9
Minor sixth, added ninth m6/9
Seventh 7, (dom7)
Minor seventh m7, min7, -7
Diminished seventh dim7, dim
Seventh, suspended fourth 7sus4, 7sus
Minor, major seventh m(maj7), m(+7)
Major seventh, flat fifth maj7♭5, maj7(-5)
Minor seventh, flat fifth m7♭5, m7(-5)
Seventh, sharp fifth +7, 7(♯5)
Seventh, flat fifth 7♭5, 7(-5)
Seventh, flat ninth 7♭9, 7(-9)
Seventh sharp ninth 7♯9, 7(♯9)
Ninth 9
Major ninth maj9, M9
Minor ninth m9, min9
Eleventh 11
Minor eleventh m11, min11
Thirteenth 13

Beginning Chords

While there are a large number of different chord types, when first starting out on guitar, you will mostly start out learning open position major chords (A, B, C, D, E ,F, G) before progressing to minor chords and then on to more complex chord shapes such as suspended and diminished chords as required.

In many cases learning the major chords and a handful of minor chords will allow you to play a large number of songs, as many popular songs consist of a relatively small number of chords e.g. many popular songs consist of just three or four chords. I’ve listed some of these below:

Song Name Artist Chords Used
Get Back The Beatles A, G, D
Twist and Shout The Beatles D, G, A
Bad Moon Rising Creedence Clearwater Revival D, G, A
Wild Thing The Troggs A, D, E
Ring of Fire Johnny Cash G, C, D
Get it on T. Rex E, A, G
Sweet Home Alabama Lynyrd Skynyrd D, C, G, F
All Apologies Nirvana C, F, G
Wanted Dead Or Alive Bon Jovi D, C, G, F
Creep Radiohead G, B, C, Cm
Knocking on Heaven’s Door Bob Dylan G, D, Am, C
The Four Seasons Vivaldi Just kidding 🙂

The list above barely scratches the surface. Most popular songs are relatively simple by nature with regard to chord structure which helps them be more memorable. Consider the nursery rhymes many of us grew up with for instance.

By understanding chord theory, you wont need to memorise hundreds of different chord shapes (although it does help to memorise the most common chords), instead you will be able to construct chords yourself based on your understanding of chord theory.

How Chords are Constructed

Chords can be constructed using intervals (the distance between two notes) or by using a formula based on the notes of the major scale.

While one can construct chords using either method, I’d recommend a basic understanding of both as each have their own strengths and weaknesses.

If you are unfamiliar with scales, I’d suggest reading this article on ‘understanding scales’ first as scales and chords really are the building blocks of music, and understanding scale theory is an important aspect of understanding chord theory.

Method 1: Chord formulas and The Major scale

We can build chords using the major scale and chord formulas. For example the chord formula for major chords is:

Major scale chord formula
1 –  3 –  5

What does that actually mean you ask?

In a practical sense this means we take the first, 3rd and 5th notes from the major scale to build a major chord. These are known as scale degrees and should not be confused with intervals e.g. major third (more on this shortly).

For example the A major scale consists of the following notes:

The A major scale
A – B – C♯ – D – E – F♯ – G♯

The first note (scale degree) is the A, the third the C♯ and the fifth is the E. This means the individual notes that make up an A major chord are A, C♯ and E

Minor chords on the other hand use the chord formula: 1, ♭3 and 5

This means the third scale degree is flattened by a semitone. This is useful in a practical sense as it means you can make any major chord a minor chord by flattening the third scale degree by one semitone.

Common chord formulas

Below is a list containing the most common the chord formulas.

Chord Type Formula
Major 1 – 3- 5
Minor 1 – ♭3 – 5
Diminished 1 – ♭3 – ♭5
Augmented 1 – 3 – ♯5
Suspended fourth 1 – 4 – 5
Added ninth 1 – 3 – 5 – 9
Minor added ninth 1 – ♭3 – 5 – 9
Fifth (partial or power chord) 1 – 5
Sixth 1 – 3 – 5 – 6
Minor sixth 1 – ♭3 – 5 – 6
Sixth, added ninth 1 – 3 – 5 – 6 – 9
Minor sixth, added ninth 1 – ♭3 – 5 – 6 – 9
Seventh 1 – 3 – 5 – 7
Minor seventh 1 – ♭3 – 5- ♭7
Diminished seventh 1-♭3-♭5-6
Seventh, suspended fourth 1 – 4 – 5 – 7
Minor, major seventh 1 – ♭3 – 5 – 7
Major seventh, flat fifth 1 – 3 -♭5 – ♭7
Minor seventh, flat fifth 1 – ♭3 -♭5 – ♭7
Seventh, sharp fifth 1 – 3 – ♯5 – ♭7
Seventh, flat fifth 1 – 3 – ♭5 – ♭7
Seventh, flat ninth 1 – 3 – 5 – ♭7 – ♭9
Seventh sharp ninth 1 – 3 – 5 – ♭7 – ♯9
Ninth 1 – 3 – 5 – ♭7 – 9
Major ninth 1 – 3 – 5 – 7 – 9
Minor ninth 1 – ♭3 – 5 – ♭7 – 9
Eleventh 1 – (3) – 5- ♭7 – (9 )- 11
* (3) and (9) are optional
Minor eleventh 1 -♭3 – 5 -♭7 – (9) – 11
* (9) is optional
Thirteenth 1-3-5-b7-(9)-(11)-13
* (9) and (11) are optional

Many of the formulas may make sense to you even if you are new to music theory. For instance the Added 9th chord, includes (as the name implies) an added ninth note of the major scale e.g. 1 – 3 – 3 – 9

A minor add9th as you may have already guessed uses the same formula, however the 3rd note of the scale is flattened a half step.

Method 2: Constructing chords using Intervals

In the iconic ‘Hallelujah’ by Leonard Cohen, the first verse tells the story of King David building a ‘secret chord’ using intervals.

Well I’ve heard there was a secret chord
That David played and it pleased the Lord
But you don’t really care for music, do you?
Well it goes like this:
The fourth, the fifth, the minor fall and the major lift
The baffled king composing Hallelujah

The ‘fourth’ and the ‘fifth’ refer to intervals. Intervals, as we already know are the distance between notes

The notes themselves are irrelevant when discussing intervals, it is the distance between the two notes that is important.

Intervals can be based on notes played sequentially e.g. one after another (melodic interval) or at the same time (harmonic interval).

Understanding intervals is critical to understanding music theory. But first, to truly understand intervals we need to understand something called the chromatic scale and how it is constructed.

The Chromatic scale

There are 12 notes in western music, and these 12 notes make up the chromatic scale. The scale below is the ‘A’ chromatic scale as the root note (and the note the scale begins on (known as the tonic) is the A.

A Chromatic scale with steps

Whole tones and semitones (whole steps and half steps)

The example above includes semitones and half tones. A semitone is the distance between two adjacent notes e.g. A to A♯ is one semitone, and is also equal to a minor second interval. While a whole tone is the distance between two adjacent notes e.g. B to C♯ and is equal to a major second interval.

This tends to make more sense when considering the layout of a piano.

Piano keyboard with steps

The white keys are whole notes e.g. C, D, E, F, G, A, and B. The black keys in between are sharps or flats e.g. C♯, D♯, F♯, G♯ and A♯

  • Sharps and flats are interchangeable e.g. a C♯ is the musical equivalent of a D♭

Only 5 of the 7 notes have sharps or flats, this is why the piano does not feature black keys between each white key. Flats or sharps can be used interchangeably. For example A♯ is the same pitch as B♭.

Why Are Intervals Important?

If we consider an A major chord, the notes that make up the chord are A, C♯, E
And while the notes themselves are clearly important, much the same as learning chord formulas it’s more effective to learn the intervals, than the notes themselves if you want to have the ability to construct chords.

The intervals for all major chords are: The first, major third and perfect fifth.

This same ‘formula’ can then be applied to all major chords. This means you only need to know the intervals of the major chord type rather than the individual notes for each chord.

How Intervals relate to each other

There are 5 categories of intervals:

  • Perfect: 5ths, 4ths, unisons and octaves
  • Major: 3rds, 6ths, 7ths
  • Minor: Flat 3rd, Flat 6th, Flat 7th
  • Augmented: Half step added to a perfect or major interval
  • Diminished: Half step reduced from a perfect or major interval

These categories relate to one another. For example a major interval when reduced by one step becomes a minor interval.

Distance Between Frets/Notes Interval Name
3 Minor Third
4 Major Third

Alternatively, If we lower a perfect interval by one step, the interval becomes a diminished interval, and a major or perfect interval if raised on half step becomes an augmented interval.

Different intervals have different names. Below is a table listing the 12 intervals, the distance between the notes or frets on the guitar neck and the interval name.

Distance Between Frets/Notes Interval Name
0 Unison
1 Minor 2nd
2 Major 2nd (Diminished third)
3 Minor 3rd (Augmented second)
4 Major 3rd (Diminished fourth)
5 Perfect 4th (Augmented third)
6 Tri-tone (Diminished fifth)
7 Perfect 5th (Diminished sixth)
8 Minor 6th (Augmented fifth)
9 Major 6th (Diminished seventh)
10 Minor 7th (Augmented sixth)
11 Major 7th
12 Perfect Octave

If you are wondering where these numbers come from as they don’t appear to correspond with the number of half steps contained within the distance between two notes, that’s because they are not supposed to. Instead they are based on the musical letters the interval passes through including the start and end note.

For example, a third is called a third because it incorporates three different letters.

Third
A  –  A♯ –  B – C – C

The letters consist of A, B and C

A Common Misconception
Chord formulas and intervals, at least in some instances will appear to be the same e.g. the major scale’s intervals are identical to the chord formula numbers based on degrees of the major scale. E.g. the third scale degree of the major scale, is also equal to a major third interval.

It’s easy, when first learning music theory to think these are the same, but it is important to understand the difference between scale degrees and intervals, despite the fact that in some instances e.g. the major scale they will appear to be of the same value.

How Intervals are named

Intervals are named by their interval type and their interval number e.g.

  • Unison
  • Seconds
  • Thirds
  • Fourths
  • Fifths
  • Sixths
  • Sevenths
  • Octaves

For example, an A major chord consists of the root note (1st), the major third and a perfect 5th.

The intervals number is based on the distance between two notes. For example, an interval of one note is known as the ‘minor 2nd’. Whereas an interval of 12 notes is known as a ‘perfect octave’.

Perfect Intervals (P)

Intervals that are either unison, 4th, 5th or a whole octave are known as perfect intervals. They remain the same whether inverted. An inverted interval is an interval that has been turned upside down e.g. the starting note becomes the final note and vice versa.

Non perfect Intervals

Non-perfect intervals are either major or minor intervals and include the second, third, sixth and seventh. Major intervals are taken from the major scale, while minor intervals are a half step lower than major intervals.

Augmented Intervals (A)

Augmented intervals are intervals that have been raised by half a step.

Diminished Intervals (d)

Diminished intervals are intervals that have been lowered by half a step.

How Major Chords are Built using Intervals

To truly understand intervals is to truly understand how to build chords. Adding intervals to the root note of a chord is how chords are built.

Let’s look at how major chords are constructed to really nail this part down, as intervals really are key to understanding how to build chords.

As already discussed, major chords consist of the root note or first, the 3rd (the 3rd is major unless otherwise indicated) and the 5th (perfect fifth) intervals.

If we build a A major chord, starting on the A (the root note) we get the following notes:

‘A’ Chromatic Scale
A  –  A♯ –  B – C – C♯ – D – D♯ – E – F – F♯ – G – G♯
  • The first note is the A.
  • A major third from the root note (4 half steps) is the C♯
  • The perfect fifth from the root (7 half steps) is the E

This means the A major chord consists of A, C♯and E

Common Chord Qualities and their Intervals

Below is a list showing the common chord qualities and their respective intervals.

Chord Type Interval Formula
Major Root – Major third (M3) – Perfect Fifth (P5)
Minor Root – minor third (m3) – Perfect Fifth (P5)
Diminished Root – minor third (m3) – Diminished fifth (dim5)
Augmented Root – Major third (M3) – Augmented Fifth (Aug5)

Summary

While there is a great deal more that could be expanded upon with regard to chords, the intention of this article is to provide an introduction to chord theory in a way that is simple for those new to guitar and music theory in general. By learning the basics e.g. what chords are, how to read chord charts, how chords are named and how chords are constructed you are building a foundation that can be built upon as your knowledge of music theory increases.

I highly recommend if you found this article useful to also check out our articles on learning all notes on the guitar fretboard along with our introduction to music scales as each will help strengthen your knowledge and help you become not only a more knowledgeable guitarist but also a better musician in general. I hope the information on guitar chord theory has been helpful, and as always if you have a question please be sure to leave a comment below.

Marty


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