Ever wonder why some chords in a key are major, some are minor, and others are diminished or 7th?
This is because of note relationships that can be learned from analyzing scales.
In this lesson we’re going to examine an aspect of music theory. This one spans the gap between scales and chords, binding the two together.
You can call the result “harmonized scales,” “diatonic chord scales,” “modal chord scales,” or any number of other things. But what’s really happening is you are outlining the chords that fit into the sound of a key simply by stacking scales.
Harmonizing a Diatonic Scale:
A diatonic scale is a scale built with a pattern that looks like:
W W H W W W H
W = Whole step, H = Half step.
This gives us a standard major scale.
In the key of C it looks like this:
C D E F G A B C
All single notes, but to harmonize them you need multiple scales working together.
Stack additional scales upon the first so that they are offset by thirds. That means from the original scale you count up three notes (including the first)
1 2 3 C D E F G A B C
From the third, start a new scale row below the first.
C D E F G A B C E F G A B C D E
Do the same thing once more to add a third scale line, starting a third up again.
C D E F G A B C E F G A B C D E G A B C D E F G
In each note column is a triad chord. From left to right they are:
If you play those chords in that order you should be able to hear an ascending sound.
Play them exactly in order though, and it will sound even more like a scale. To do that you would play a C triad then move each note in the triad up a half or whole step according to the scale.
| | C Dm Em F G Am B° C A |-------------------------- E |-0--1--3--5--7--8--10--12- C |-0--2--4--5--7--9--11--12- G |-0--2--4--5--7--9--10--12-
The distances between the different notes in a scale are the reason we end up with the chord types in that order.
Some of the intervals are minor thirds and some are major thirds. Using this method to find the chords that are closely related to the key can be kind of tedious (writing out and lining up the scales). Instead, there is a formula you can draw from the above list of chords.
Just like you can figure out a chord’s formula in reverse, you can put a simple formula on a chord scale.
It goes like this:
I ii iii IV V vi vii° I
The upper-case numbers are major chords, the lower-case numbers are minor chords, and the 7th chord is diminished.
You can also just use Roman numerals and add an “m” to denote a minor chord.
I IIm IIIm IV V VIm VII° I
With this formula you can figure out what chords work best with any key.
For example, to find the chords in the key of G, you would go through the above steps, only with the G major scale instead of C major.
I IIm IIIm IV V VIm VII° I G Am Bm C D Em F#° G
Or with the key of E:
I IIm IIIm IV V VIm VII° I E F#m G#m A B C#m D#° E
Of course, this doesn’t apply to the exceptions like a Hawaiian vamp when you use a II7 chord, or a rock song where you use the bVII, but if you are playing diatonic melodies, this formula will tell you what chords you can use.
To find the relative chords for a minor scale, you would use the same formula started on the sixth note. The chord names wrap around, but you would start the roman numerals from the beginning:
i ii° III iv v VI VII i Am B° C Dm Em F G Am
Im II° III IVm Vm VI VII Im