Guitar Chord Theory

Many guitarists play chords without ever knowing how they are constructed and why they sound the way they do. While there is nothing wrong with this, knowing basic guitar chord theory can increase your understanding and enjoyment of the music that you play.

Writing songs and riffs by ear is a great skill, and one which should be encouraged. However, knowing how music works can improve your songwriting and composing, and will also speed up the process. So, if you’ve ever wondered what all of the numbers and symbols in guitar chords mean, then read on…

Guitar Chord Theory – Part One

The first part of this article will introduce some basic guitar chord theory. The next part will go on to cover some more advanced concepts. You should also refer to the diatonic chords article for further information on chord theory.

There is a lot of information contained on this page, so be sure to bookmark it so you can refer to it whenever you need to. We recommend that you work through the articles slowly, and try out the chords with a guitar, so you know how they sound.

Major And Minor Chords

A basic but important aspect of guitar chord theory is the difference between major and minor chords. Most guitarists know that major chords sound ‘happy’ and the minor chords sound ‘sad’. The difference between the two types of chord is down to one note. Minor chords contain the note that is a minor third from the root note of the chord. Major chords contain the note a major third away from the root note.

The terms ‘major third’ and ‘minor third’ refer to intervals between the notes and the root note of the chord. See the table below for a list of all of the intervals used in chord construction.

Play the basic major and minor triad chords below on your guitar, and notice how moving the note on the 4th (D) string just one fret lower changes the whole sound of the chord.

Chords can be constructed with many more than three notes, but whether they are ‘major’ or ‘minor’ all comes down to whether there is a major third or minor third present.

Some Definitions, Intervals And Scale Spelling

The root note of a chord is the note that the chord is named after, e.g. the C in C major.

Throughout these guitar chord theory articles, you will be hearing about thirds, fifths, etc. These are ‘intervals’ – i.e. the distances between two notes. The numbers in chord symbols represent the intervals between notes contained within the chord and the root note of the chord.

The Guitar Chord Intervals Chart below shows note intervals with a root note of C.

Diminished And Augmented Chords

Triads are basic three note chords. Major and minor triads are shown above. The two other kinds of triad are the diminished and augmented triad.

Diminished triads are made up of the root note, the minor third and the flattened (diminished) fifth note. The symbol for a diminished chord is a small circle. Diminished triads are often extended to include the note a minor third above the diminished fifth note; these chords are known as diminished sevenths.

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Augmented triads include the root notes, the major third and the sharpened (augmented) fifth note. The symbol for an augmented chord is a plus sign. A chord symbol which includes a plus sign shows that the chord has a sharpened (augmented) fifth, regardless of the other notes it contains.

Guitar Chord Theory – Inversions

Chords can be played as inversions. This is when a note other than the root note is used as the bass note of the chord.

Read more about chord inversions here.

Slash Chords

Slash chords specify the bass note for a chord. Slash chord symbols show both the chord to be played and (after the slash) the bass note that should be added.

Sometimes the bass note is already part of the chord, in which case the slash chord is showing an inverted chord (e.g. C/G, in which G is already part of a C major chord).

At other times the slash chord shows that the bass note should be a note not already contained within the chord (e.g. Dm/C, in which the chord is D minor, and the bass note is a C).

Suspended And ‘Added’ Chords

Suspended Chords

In guitar chord theory, a suspended chord is one whose third has been replaced by either a perfect fourth or a major second. Remember that the terms ‘second’ and ‘fourth’, etc., mean how far notes are from the root note of the chord. In a Sus4 chord, the third (either major or minor) is replaced with the fourth.

In a sus2 chord, the third is replaced with the second.

Added Chords

Added chords are simply major or minor chords with additional notes. The most common added chord is an add9. This is a major chord with a ninth added to it.

Notes in a C major chord: C E G

Notes in a Cadd9 chord: C E G D

The dissonance in added chords can be very pleasing to the ear. Added chords are often used to replace standard major chords when a more ‘colorful’ sound is needed.

The difference between an added chord and a suspended chord is a little blurred. Occasionally sus chords do contain the third notes, as well as the fourth or second added notes.

Ninth Or Second?

Notice that a ‘ninth’ note is the same as a ‘second’ note. If the root note is a C, then the second and ninth notes would both be a D. The term ‘add9’ is usually used for chords that also contain a third, whereas a ‘sus2’ chord usually does not contain a third.

Dominant ninth chords (usually shortened to just ‘ninth’ chords) always contain a minor seventh note in addition to the ninth note. Dominant chords are discussed in part two of this article.

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Sixth Chords

Sixth chords are the same as added sixth chords. They can be major or minor, in which case they are also known as major 6th and minor 6th chords respectively.

Notes in C major 6th chord: C E G A

Notes in C minor 6th chord: C Eb G A

Learn more about 6th chords here.

Guitar Chord Theory Conclusion

If you’ve gotten this far, congratulations. Learning guitar chord theory is a challenge, but worthwhile if you want to gain a broader picture of how music works. You can learn more about the fundamentals of music theory at wikipedia.

In the second part of this series, we introduce dominant chords, and show you how to understand the complex chord symbols used in jazz and other styles of music.