This post is one of a 2-part series of free basic music theory lessons on my blog, musictheoryde-mystified.com. You can see the complete list here. Please feel welcome to make a comment or ask a question.
The overall key of a piece is called the home key. The chords that sound best together are those that are closely related to the home key.
As we saw in B19. Relative/Functional Chord Notation, the chord on the root note of the home key is called the tonic chord. The chords we’re going to look at are so closely related to the tonic chord that all their notes belong to the home key.
The Chords of the Major Scale
One way to find these chords is to write out the scale of the home key starting on the root note, then again starting on the 3rd and on the 5th. Since we’re talking about major keys, we’ll use C major as an example.
Let’s see which chords we end up with…
- We can see that the tonic, subdominant and dominant chords, I, IV and V, are major chords.
- The supertonic, mediant and submediant, chords ii, iii and vi, are minor chords.
- The chord on the leading note isn’t a major or minor chord as it doesn’t have a perfect 5th, so it acts quite differently to the others. We’ll leave it out for now and come back to it in the next lesson.
Closely Related Chords Are In Closely Related Keys
As it turns out, the dominant, V, is the chord of the next key in the cycle of 5ths and the subdominant, IV, is the chord of the previous key in the cycle of 5ths.
This should be no surprise. A major or minor chord represents a key so the most closely related chords are those of the most closely related keys.
Just these three chords alone form the basis of many popular songs and tunes.
Chords ii, iii, and vi are the relative minors of the subdominant, dominant and tonic chords respectively.
Being in a different mode, they are slightly less directly related to the home key than the three major chords, lending a degree of sophistication when included.
The chords of the major scale are those of the home key, next and previous keys in the cycle of 5ths and their relative minors. All the notes in each of these chords are notes of the home key.
The 6 Most Useful Chords In Any Major Key
The chords of the major scale fit together so well that they can be played in any order and still sound musical. As long as the tonic chord appears every now and then, we can feel the overall key of the music by the way these chords support each other.
If you look at any piece of sheet music with chord symbols such as a song lead sheet, assuming it’s in a major key, you’ll see that the majority of the chords are the chords of the major scale. They may have a suffix indicating added 7ths or other notes, but at their core they are still the chords of the major scale.
What About Minor Keys?
Minor keys are a little more complicated because of prevalence of the melodic and harmonic minors. The accidentals in these scales produce different chords than the natural minor.
We’ll look at the chords of the minor scale in my intermediate music theory short course, planned for 2023.
Chords For Other Modes
The same approach of writing a scale on the 1st, 3rd and 5th can be used to find closely related chords of any mode.
All the traditional Western modes will produce 3 major chords and 3 minor chords.
Try These…
Name the 6 chords of the major scale in the following keys; 3 major chords and their relative minors.
I, IV and V are the most common, so in the example I’ve listed these first.
I’ve listed the chords in the 2nd row starting with vi because that matches the order of the major chords: vi is the relative minor of I, ii is the relative minor of IV and iii is the relative minor of V.
Example
G major
I = G, IV = C, V = D
vi = Em, ii = Am, iii = Bm
- D major
- F major
- E major
- Ab major
Answers at the end of this post.
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PART 2 CONTENTS: Basic Music Theory Course Contents
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Answers to Try These…
D major
I = D, IV = G, V = A
vi = Bm, ii = Em, iii = F#m
F major
I = F, IV = Bb, V = C
vi = Dm, ii = Gm, iii = Am
E major
I = E, IV = A, V = B
vi = C#m, ii = F#m, iii = G#m
Ab major
I = Ab, IV = Db, V = Eb
vi = Fm, ii = Bbm, iii = C/m