Chord Scales

If you’ve read and understand the how to build scales and how to build chords lessons, you can move onto another related aspect of music theory. This concept spans the gap between scales and chords and is called “chord scales” or “modal chord scales” (brilliant!). Ever wonder why in a certain key some chords are usually major, some are minor, and others are diminished (or usually just a 7th)? Did you also notice that these chords all use the notes from the key-scale? Here’s why:

You build a scale with the WWHWWWH technique and end up with a major scale (or minor if you change the starting point). In the key of C it looks like this:

C D E F G A B C

Those are all single notes, but if we want to turn each note into a chord here’s what would happen:

You stack the key-scale so that it is offset by thirds. Start with a normal scale at the root:

C D E F G A B C

Then take the scale started from the third note:

C D E F G A B C
| | E F G A B C D E

Then you add a third scale started on the fifth note (a third up from the start of the second scale):

C D E F G A B C
| | E F G A B C D E
| | | | G A B C D E F G

Now line them all up:

C D E F G A B C
E F G A B C D E
G A B C D E F G

…and examine your chord scale.

Each column is a triad chord. In the example they are:

  1. C
  2. Dm
  3. Em
  4. F
  5. G
  6. Am
  7. B°
  8. …Back to C

If you play those chords in that order you should be able to hear an ascending sound. You can make it sound a lot more like a scale though if you play it in ascending triads. 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 – up to Dm then again to Em and so forth. Like this:

| | 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 capital 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 for the most part, if you are playing simple major 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

Or…

Im II° III IVm Vm VI VII Im