Harmonizing the Major Scale II: Seventh Chords

The process of harmonizing a scale involves building chords on each degree (note) of the scale, using only notes from that scale.

This post will:

Take us through the process of harmonizing the major scale with seventh chords.
Analyze the chords that result, along with the Roman numerals assigned to each chord.
Show the relationship between the chords in a harmonized major scale and the the scale itself.
Provide instruction on how that relationship relates to soloing on a guitar.

Harmonizing a Major Scale with Seventh Chords

To harmonize a scale with seventh chords, we need to take each note in the scale and add three notes above it, each one three scale steps higher.

Harmonizing a C Major Scale

We already added two of the three notes needed when we harmonized a C major scale with triads (fig.1).

Fig.1

Now all we need to do is add another note to each chord, the note three scale steps higher than the last one added.

Harmonizing the First Scale Degree

To the C in the scale, we have already added an E and a G. To complete the seventh chord, we need to add a B (fig.2).

The distance between the G and the B is three scale steps (G, A and B).

Fig.2

Harmonizing the Second Scale Degree

To the D in the scale, we have already added an F and an A. To complete the seventh chord, we need to add a C (fig.3).

The distance between the A and the C is three scale steps (A, B and C).

Fig.3

Harmonizing the Third Scale Degree

To the E in the scale, we have already added a G and a B. To complete the seventh chord, we need to add a D (fig.4).

The distance between the B and the D is three scale steps (B, C and D).

Fig.4

Harmonizing the Fourth Scale Degree

To the F in the scale, we have already added an A and a C. To complete the seventh chord, we need to add an E (fig.5).

The distance between the C and the E is three scale steps (C, D and E).

Fig.5

Harmonizing the Fifth Scale Degree

To the G in the scale, we have already added a B and a D. To complete the seventh chord, we need to add an F (fig.6).

The distance between the D and the F is three scale steps (D, E and F).

Fig.6

Harmonizing the Sixth Scale Degree

To the A in the scale, we have already added a C and an E. To complete the seventh chord, we need to add a G (fig.7).

The distance between the E and the G is three scale steps (E, F and G).

Fig.7

Harmonizing the Seventh Scale Degree

To the B in the scale, we have already added a D and an F. To complete the seventh chord, we need to add an A (fig.8).

The distance between the F and the A is three scale steps (F, G and A).

We now have a fully harmonized C major scale with seventh chords.

Fig.8

Chord Analysis

Now that we have harmonized a C major scale (we have built chords on each degree of the scale), we can determine the quality of each seventh chord using the chord formulas detailed in the post entitled Seventh Chords.

An analysis of each chord is provided below:

The first chord contains the notes C, E, G and B — the first, third, fifth and seventh degrees of a C major scale, so the first chord is Cmaj7 (fig.9a).
The second chord contains the notes D, F, A and C — the first, flatted third, fifth and flatted seventh degrees of a D major scale, so the second chord is Dm7 (fig.9b).
The third chord contains the notes E, G, B and D — the first, flatted third, fifth and flatted seventh degrees of an E major scale, so the third chord is Em7 (fig.9c).
The fourth chord contains the notes F, A, C and E — the first, third, fifth and seventh degrees of an F major scale, so the fourth chord is Fmaj7 (fig.9d).
The fifth chord contains the notes G, B, D and F — the first, third, fifth and flatted seventh degrees of a G major scale, so the fifth chord is G7 (fig.9e).
The sixth chord contains the notes A, C, E and G — the first, flatted third, fifth and flatted seventh degrees of an A major scale, so the sixth chord is Am7 (fig.9f).
The seventh chord contains the notes B, D, F and A — the first, flatted third, flatted fifth and flatted seventh degrees of a B major scale, so the seventh chord is Bm7(b5) (fig.9g).

Fig.9

Diatonic Chords

The term diatonic refers to notes and chords found within a scale or key.

The chords that result from harmonizing a scale are considered diatonic (or natural) to that scale and key.

The chords we built above — using only notes from a C major scale — are diatonic to the key of C major. In other words, the notes contained in the chords are all found within a C major scale.

For example:

An Am7 chord is diatonic to the key of C major because the notes A, C, E and G are all found within a C major scale.
An Fmaj7 chord is diatonic to the key of C major because the notes F, A, C and E are all found within a C major scale.

Roman Numerals

Every major scale has seven seventh chords that are diatonic to it, one chord for each scale degree.

Each of the seven diatonic chords is assigned a Roman numeral, which reflects the chord’s position within the key, relative to the tonal center (the first note or chord):

Uppercase numerals are used for major seventh and dominant seventh chords.
Lowercase numerals are used for minor seventh and minor seventh, flat five (or half diminished) chords.

Additional Notation

The Roman numerals representing each chord type are followed by additional notation:

The uppercase numerals representing major seventh chords are followed by maj7.
The lowercase numerals representing minor seventh chords are followed by the number 7.
The uppercase numerals representing dominant seventh chords are followed by the number 7.
The lowercase numerals representing minor seventh, flat five (or half diminished) chords are followed by small circle with a diagonal line through it and the number 7.

The Roman numerals representing the seventh chords diatonic to the key of C major are shown in fig.10.

Fig.10

Sequence of Chords

Every harmonized major scale has the same sequence of seventh chords. As the sequence of chords is the same in every key, the sequence of Roman numerals is also identical.

In any given major scale or key, the seventh chord qualities are as follows:

The I and IV chords are major seventh.
The V chord is dominant seventh.
The ii, iii and vi chords are minor seventh.
The vii chord is minor seventh, flat five (or half diminished).

All 12 Harmonized Major Scales

All 12 harmonized major scales are shown in fig.11.

Fig.11

Soloing Application

You can use a major scale to solo over any of the chords that are diatonic to it because the notes generally won’t clash with the chords.

And if all of the chords in a progression are diatonic to the same major scale, you can use that scale to solo over the entire progression.

For example, if all of the chords in a progression are diatonic to a C major scale, you can use a C major scale to solo over the progression.

The progression in fig.12 contains four chords all diatonic to a C major scale. So you can use a C major scale to solo over the progression.

In the key of C major:

Cmaj7 is the Imaj7 chord.
Am7 is the vi7 chord.
Dm7 is the ii7 chord.
G7 is the V7 chord.

Fig.12