Dansm's Guitar Chord Theory
Chord Theory

Chords are the basis of all Western music. They are absolutely crucial to the guitar and to rock music, and an understanding of chords will improve your understanding of the guitar and music immensely. This page is designed to help you with the music theory behind chords, so sit back and prepare to learn more about your instrument in the next ten minutes than you have in the past month. Before you begin, check out my page on intervals because this information will be used here. On this page I will discuss the basics of scales because scales are important for chord formation, but I will not cover them in depth because I have a full page on scales.
The figure below shows the twelve notes of the chromatic scale. These are the only notes used in Western music. Notes such as D# and Eb represent the same pitch and are called enharmonic equivalents. Different enharmonic equivalents are used in different scales; the sharp is used for sharp keys (e.g. F# major), and the flat is used in flat keys (Ab major).

The interval between each of the notes shown above (G and G#, for example) is one half step. Each fret on your guitar is equivalent to one half step; twelve half steps make an octave. As you learned in my page on intervals, two frets (two half steps) make a whole step. The distance between G and A is a whole step. As a framework for studying major/minor/diminished chords, I will use the major scale. The major scale is made up of the following pattern of whole and half steps:

The notes of the scale are referred to as "root" (or "tonic"), "second," "third," "fourth," etc., as shown on the diagram below. This will be very important when we start constructing chords in the next several pages. Note that when we say "D is the fourth of A," you count A as 1, B as 2, C# as 3, and D as 4.

All basic chords you play are made up of three pitches: the root, third, and fifth. Variations on the theme will be discussed on other pages, but all major, minor, and diminished chords contain these three notes. If you look at the diagram and try to build a chord on the note A, you pick out the first (or root), third, and fifth notes of the scale: A-C#-E. This is shown in the diagram below:

To build a chord on the note B, pick out the root, third, and fifth starting with B, and you get B-D-F#:

But why is the A a major chord, and why is the B a minor chord? This comes about because of the pattern of half and whole steps in the scale. Whether a chord is major or minor depends on the interval, or musical distance, between the root and third, and the root and fifth. Check out my page on intervals for more information on them.

The major chord contains four half steps between the root and the third (a major third), and seven half steps between the root and fifth (a perfect fifth). The major chord follows the pattern 1-3-5.

minor chord contains three half steps between the root and third (a minor third), and the same perfect fifth between the root and fifth. The minor chord follows the pattern 1-m3-5.
If you try to build a chord on the G#, the three pitches are G#-B-D. The interval between G# and B is a minor third, but the interval between G# and D is not a perfect fifth (seven half steps), it is six half steps. This interval is called a diminished fifth, and is a rather unstable interval. This is why this G# chord is called a diminished chord: it contains a diminished fifth instead of a perfect fifth.

The diminished chord contains three half steps between the root and third (a minor third), and six half steps between the root and fifth (a diminished fifth). The diminished chord follows the pattern 1-m3-d5.

The G# chord and C# chord shown below are played just like barre chords, and can be moved to whichever fret is necessary. Simply notice the bass note of the G# is on the sixth string and the bass note of the C# is on the fifth string. For more information on barre chord theory, click here.


As you may recall from the chord-leading lesson, diminished chords pull strongly toward the major chord a half step higher, so the G# pulls toward A and C# pulls toward D. These chords are not frequently used in popular music, so it is not imperative that you know how to play them, but if you ever come across one you will know what you are dealing with.
This concludes the lesson on major/minor/diminished chords. Knowing the theory behind these chords is a very valuable skill which can be applied to songwriting, figuring out songs, etc. Study this lesson and the others in this series, and it will make you a better, more knowledgeable guitarist. I suggest moving on to my discussion of chords in major keys to complete your understanding of chords in keys. Enjoy!
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1997 Daniel E. Smith.