Chord Construction Part 2: Triads and Stacking 3rd's

(For this lesson, remember that the terms: Minor 3rd, Minor 3, m3, and b3 all mean the same thing.)

In Part One we learned about a two note chord named a Power Chord. Now we will look more in-depth at the three note chords named: Triads.

Two of the most common Triads are the plain Major and Minor Chords, the Formulas shown below are shown from a couple of different Root notes (use the references below for the Note Name relationship to the Interval Name):

Major Chord (triad) = R M3 5
C (Major Chord) = C E G
G (Major Chord) = G B D
A (Major Chord) = A C# E
F# (Major Chord) = F# A# C#

Minor Chord (triad) = R b3 5
Cm (Minor Chord) = C Eb G
Gm (Minor Chord) = G Bb D
Am (Minor Chord) = A C E
F#m (Minor Chord) = F# A C#

Here's a common way to play these Triads (these are movable chords, the Root or Note Name of the chord is whatever fret/note you are playing on the D string):

A Major

--x--
--5-- = 5 = E
--6-- = M3 = C#
--7-- = R = A
--x--
--x--

Am

--x--
--5-- = 5 = E
--5-- = b3 = C
--7-- = R = A
--x--
--x--

From the formulas and the different chord name examples, you can see that the difference between Major and Minor Chords/Triads is the M3 and b3, respectively. So, this should lead you to believe that the "3rd" in a chord is a very important note/interval to determining the "sound" of the chord, and what to call the chord.

This is important so let me repeat:

...the "3rd" in a chord is a very important note/interval to determining the "sound" of the chord, and what to call the chord.

The 3rd is the determining factor to knowing whether the chord is Major or Minor.

What happens if I take these two basic Triads and change the 5 in someway?

Well, for that question we could change the 5 by flatting it, or by sharp'ing it I guess. By doing this we can form two other basic, but important, triads:

Augmented Triad (also known as an aug, +5, or a #5 chord) = R M3 #5
Diminished Triad (also known as m-5, or a mb5 chord) = R b3 b5

Here's a common way to play these Triads (these are movable chords, the Root or Note Name of the chord is whatever fret/note you are playing on the D string):

Aaug, A+5, A#5, A augmented:

--x--
--6-- = #5 = F
--6-- = M3 = C#
--7-- = R = A
--x--
--x--

Am-5, Amb5, A diminished triad:

--x--
--4-- = b5 = Eb
--5-- = b3 = C
--7-- = R = A
--x--
--x--

Now we know four basic Triads:

Major = R M3 5
Minor = R b3 5
Augmented = R M3 #5
Diminished = R b3 b5

And, we learned a movable pattern, with the Root on the D string, to play for each Triad.

Compare the four movable patterns I've presented to see how the notes change in relation to each other chord. This is key to understanding their relation to each other and to visually start to pick out Intervals/Triads on the fretboard.

Hopefully these are understandable at this point.