Chord Scale Theory

Now that we have talked a little about intervals, triads, and seventh chords, let’s continue with our discussion of scales.

A little review

A chord is any 3 or more notes that are played simultaneously.
A triad is a 3-note chord usually built in thirds; it contains a 3rd and 5th above the root.
Triads are tertian chords meaning they are built of intervals of a 3rd.
A seventh chord is a 4-note chord consisting of a 3rd, 5th, and a seventh above the root of the chord.
Triads and seventh chords can occur in root position (the root is in the bass) or with any other note of the chord in the bass (an inversion of the chord).

In our discussion of major scales, we indicate the scale, the scale degrees under the notes (from 1-8 and 9, 11, 13), and a chord coming from the scale.

Chord scale theory

The idea that a scale comes from a chord or that a chord is contained in a scale isa theory called chord-scale theory.

The chord that comes from/is contained in a scale is usually thought of as a seventh chord (with markings for the extended tertian chord — 9, 11 and 13 chords).

To Demonstrate

Below is the 2-octave C major scale with scale degrees that we had above.

If we start on the first note of the scale and, instead of going up by steps we ascend by 3rds (creating a very extended tertian chord (a 13th chord), we get the following:

Arranging these notes in ascending order, we get:

Thus, a scale can come from a chord.

Chord scale theory in C major scale

To emphasize this chord scale theory, we show the seventh chord chord coming from the scale each time we write a scale (with designations for the 9, 11, and 13 in parentheses).

For example:

The bottom note of the chord will always be the first note of the scale and the other notes of the chord are the thirds above that note from the scale that create the extended chord.

Therefore, in a major scale, the chord will contain the 1, 3, 5, and 7 scale degrees, creating a major-major seventh chord. The numbers in parentheses after the chord name indicate that there would be a 9, 11, and 13 with no alterations if the chord were extended.