Major triad
The first triad I would like to talk to you about is a major triad. As I mentioned in the introduction to chords, a triad is a collection of 3 notes stacked in 3rds.
The formula to make a major triad is:
major 3rd + minor 3rd (from the root of the triad)
Let's take a look at a C major triad. First, you have a C, then you go up by a major 3rd to an E, then you go up by a minor 3rd to a G.
These are some examples of major triads. As you would notice, the first interval from the root is a major 3rd, then a minor 3rd follows.
Minor triad
The formula to make a minor triad is:
minor 3rd + major 3rd (from the root of the triad)
Let's make a A minor triad. First we start with an A, then go up by a minor 3rd to a C, then we go up by a major 3rd to an E.
These are some examples of minor triads.
Diminished triad
The formula to make a diminished triad is:
minor 3rd + minor 3rd (from the root of the triad)
Let's make a B diminished triad. We start with a B, then go up by a minor 3rd to a D, then another minor 3rd to an F.
Here are examples of diminished triads.
Augmented triad
The formula to make an augmented triad is:
major 3rd + major 3rd (from the root of the triad)
Let's take a look at how a G augmented triad is made. It starts with a G, then up by a major 3rd to a B, then another major 3rd up to a D#.
Here are some examples of augmented triads.
Interval of the outer two notes
You will notice this one thing when you think about the intervals of the outer two notes of each triad.
Triad
Outer Interval
Major triad
Perfect 5th
Minor triad
Perfect 5th
Diminished triad
Diminished 5th
Augmented triad
Augmented 5th
The outer interval of a diminished triad is a diminished 5th. The outer interval of an augmented triad is an augmented 5th. Knowing this will make it easier to identify triads.
Summary
Here is a summary of how to make different kinds of triads.
Major Triad: major 3rd + minor 3rd
Minor Triad: minor 3rd + major 3rd
Diminished Triad: minor 3rd + minor 3rd
Augmented Triad: major 3rd + major 3rd
These 4 types of the chords are the most important ones we should know.