The three primary chords
How do you harmonize a melody? It helps to know that in any key there are three chords that are especially important. Those are the chords built on the first, fourth and fifth notes of the scale.
Another way of saying it is that the primary and major triads are the most important triads in a key built on scale degrees 1, 4, and 5 of the major scale. They are called the Primary Triads or Primary Chords of the tonality and are identified with the Roman Numerals I, IV and V. These three triads contain all the tones of the major scale.
For example, the C Major Scale is: CDEFGABC. Of these 8 notes (excluding the perfect 8th; C), 3 of them are Primary or Major Triads. In the C major scale the roots of the three primary chords are I, IV, and V, which are C (CEG), F (FAC), and G (GBD).
As you will learn later, the other notes in the scale are associated with other types of chords, such as minor and diminished.
Primary chords are major chords because they consist of the root, a major third, and a perfect fifth. So here is a formula to remember:
Major Third + Perfect Fifth = Major Chord
Why are major scales important to understanding primary chords? If we hadn’t known the C major scale, how would we have known that E is the major third and G is the perfect fifth of C major?
Well, there are two ways to form a major triad:
First select notes 1, 3 and 5 of a major scale. This is the easiest way if you know your major scales. In the key of F major, F is the first note, A is the third note, and C is the fifth note. F, A, C form the chord of F Major. The same rule applies to all 12 keys.
Second, another way to form a major chord (triad) is to add the interval of a minor third on top of a major third. If you know that a minor third equals 3 semitones and a major third equals 4 semitones (or 2 whole steps), you’re on your way to applying music theory.
For example, C to Eb (minor third) is 3 semitones. C to C# = 1 semitone. C to D = 2 semitones and C to Eb = 3 semitones. So, to make a major chord, just place a minor 3rd on top of a major 3rd.
Here’s the secret:
Let’s say you want to build a G major chord. Start at G (the root) and add a major third (4 half steps), G + B, then add a minor third (3 half steps) on top of that (from B), G + B + D. From G to B is a major triad and from B to D is a minor third. This makes a G major chord.
Songs that begin with major chords are Mary Had a Little Lamb, Are You Sleeping? and Go tell it on the mountain.
In major keys, chords built on I and IV are major chords. The V chord can be a major or dominant seventh. So, the three primary chords in C major: C major (CEG), F major (FAC), and G7 (GBDF).
Those three chords will suffice for the harmonization of many simple melodies. In many others they serve as the backbone of harmony. It is not possible to set hard and fast rules for harmonizing a melody. Many times your ear should be your guide.
But ordinarily the main notes of the melody will be present in the chords that accompany them. What I do is play the chords in my left hand and put chord tones in my right hand, under the melody.
Because the I, IV, and V7 chords are so important, it pays to become familiar with their positions on the keyboard. By practicing this exercise in all major keys, you will be taking an important first step in developing the ability to harmonize melodies on the keyboard.
If you read chord charts, you would harmonize the melody like this:
C/EGC
F/FAC
G/DFGB
C/EGC
C/GEC
F/ACF
G/DFGB
C/GEC
C/CEG
F/CFA
G/BDFG
C/CEG
I wish you all the best in your chord studies. These 3 primary chords in any key are a good start for putting together progressions that make for familiar songs to enjoy.
