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Theory 101: Triads



Triads are 3-note chords whose notes are stacked in thirds, meaning each chord tone is a third interval away from its neighboring note.


Let’s look at the C triad to illustrate.


If we write out the musical alphabet, we get:

A, B, C, D, E, F, G.


To build a C triad, we start with note C.  If we designate this as the first note in a sequence, and number the remaining letters this way, we get:


C, D, E, F, G

1   2   3


Now, if count up 3 notes with C being number 1, we would be moving up a third, to the note E.


So now we have the first 2 notes of a C triad: C-E


If we do this again and move up another third from E,


E, F, G

1  2  3


we get the note G.


Now we have spelled out a triad C major: C-E-G.



No matter the root of a triad, the chord tones will always be a third away from neighboring chord tones, ie all triads are built in thirds.


Below are some more triads.  Notice every chord tone is a third away from its neighbor:


A minor triad: 


A, B, C, D, E, F, G


B diminished triad: 


A, B, C, D, E, F, G


F major triad: 


F, G, A, B, C, D, E, F, G




The Chord Tone Names

Now that we’ve looked at how triads are made up of three notes stacked in thirds, let's move on to the chords tone names (ie the names of each note in the chord).


The note C in a C triad is known as the root, it is the fundamental note, the note from which the rest of the chord is built.  We use the letter “R” to symbolize it.


Next, we have the note E.  In a C triad the is E is called a third. The third is the chord tone that gives any chord its quality, meaning it determines whether a chord is major or minor.


Finally, we have the note G which in our example is the 5th.


We can write out the chord tones of a (major) triad like this:




If we number each letter starting from the root, this idea becomes more clear:


C, D, E, F, G

1   2   3  4   5

R       3       5


Figure 1 is a common (major) triad voicing played on the guitar.











Chord quality

The quality of a chord is determined by the third of the chord.  If the third is four half-steps above the root, then the third is said to be a natural third, making the triad major.   (The smallest distance between any two notes is called a half-step.  On the guitar, that would be two notes that are one fret apart.)


If the third is three half-steps above the root, then the third is said to be a flatted third, making the triad minor.


Minor triads are symbolized this way:




Below is a common minor triad played on the guitar.  If we compare it to the major triad fingering above, notice the flatted third is one half-step lower than the natural third of the major triad.













The 5th

In the above examples, we see that a third can either be natural or flatted.  Similarly, there are several types of 5ths: the perfect 5th, diminished 5th, augmented 5th.


Perfect 5th - is five note names from the root ie,


C, D, E, F, G

1   2   3  4  5



and 7 half steps away from the root.  Triads with perfect fifths sound stable and are common in pop music.


Diminished 5th - is five note names from the root and 6 half steps away.  Triads with diminished fifths sound darker and angular.


Augmented 5th - is five note names from the root and 8 half steps away.  Triads with augmented fifths have a bright but quirky sound.


(These descriptions are, of course, subjective.)


Below are major chords with diminished or augmented 5ths.


R-3-b5 - if C were the root, the notes would be C-E-Gb

R-3-#5 - if C were the root, the notes would be C-E-G#


Using the chord diagram in Figure 1 as a reference, how would you play the following chords?


1.) R-3-b5

2.) R-3-#5

3.) R-b3-b5




For more on theory and harmony and how to apply them to the guitar, look into SFGA’s music theory products and programs.

Major Triad
Minor Triad
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