We know that a chord is any number of notes sounded simultaneously. Well a triad is a three note chord.
We're going to start by looking at the tonic triad. You remember the technical names
used to describe
the position of a note in the scale. The tonic is of course the first note or root of a scale. So to build a tonic triad
we will be starting with this note.
Let's take the key of D major as an example. Here's the tonic of D major:
So here's the rule:
To build a triad we start from our root note, and add the third and the fifth above.
So here is the tonic triad in D major:
Here's how we found those notes:
D is our root note.
Three notes up the D major scale from D (counting D as note 1) gets us to F sharp - the 3rd
Five notes up the D major scale from D gets us to A - the 5th
Any note with this 1-3-5 structure is called a TRIAD
A triad built on the first note of the scale is called the TONIC TRIAD
You can build such triads in any key - major or minor, using the same procedure of simply counting up the scale notes 1, 3 and 5.
Here are a few examples: