Learning how to construct chords and scales is maybe the most important skill in our journey when learning to think about our instrument better, and to become a really expressive and thoughtful musician.
All chord and scale tones are based on the tones of the major scale. The "R" or root note represents the 1st note of the major scale, and all other tones are calculated starting with the root.
Major chords are constructed with the 1st, 3rd, and 5th notes of the Major scale. Take a look at the diagrams below that compare the C, D, and E Major scales and their corresponding Major triads. A triad is the simplest form of a chord, containing just 3 notes.
C Major scale
Minor chords are built with the 1st, b3rd, and 5th notes of the Major scale. A "b3rd" is a 3rd that has been lowered by one half step. Let's see what that looks like on both the staff and the guitar fretboard by comparing the Major triads from the previous examples with a Minor triad from the same root note.
C Major Triad
Now that we know the basics, we can start really Thinking. Let's look at constructing chord types that are different than just Major and Minor.
2 chords, also called "sus2," are constructed with the 1st, 2nd, and 5th notes of the Major scale.
sus chords, also called "sus4," are constructed with the 1st, 4th, and 5th notes of the Major scale.
C Major scale
Let's look at barre chord versions of these same chord types. These chord shapes will have more than just three notes, and will be more practical. Some of the chord tones will be repeated in some of these shapes which is very common!
To recap:
Major chords are constructed with the 1st, 3rd, and 5th notes of the Major scale
Minor chords are constructed with the 1st, b3rd, and 5th notes of the Major scale
2 chords are constructed with the 1st, 2nd, and 5th notes of the Major scale
sus chords are constructed with the 1st, 4th, and 5th notes of the Major scale
Moving forward. Now let's go beyond 3 chord tones.
6 chords are constructed with the 1st, 3rd, 5th, and 6th notes of the Major scale
maj7 (major seventh) chords are constructed with the 1st, 3rd, 5th, and 7th notes of the major scale
7 (dominant seventh) chords are constructed with the 1st, 3rd, 5th, and b7th notes of the Major scale
min7 (minor seventh) chords are constructed with the 1st, b3rd, 5th, and b7th notes of the Major scale