Key Center Soloing III: Identifying the Major Key Centers

In my last two posts (Key Center Soloing I and II) we analyzed various chord progressions to determine their key centers and which scales to use to solo over the progressions.

For each progression, we listed all the keys each chord belongs to, and then we identified the common one.

There are several ways to determine the key centers for any given chord. This post will provide instruction on how to use your guitar to identify the major key centers for any given chord.

Identifying Major Key Centers

One way to identify the possible key centers for any given chord is to refer to my posts that include all 12 harmonized major scales and look for the ones that the chord belongs to. There is also a numerical formula that works.

But the fastest and easiest way is to simply look at a guitar because the roots of the diatonic chords in any given key are always on the same frets, relative to one another.

I will use the first chord progression in Key Center Soloing I to illustrate the process.

Major Key Chord Progression

The progression in fig.1 includes four triads — C, Am, Dm and G.

Fig.1

Major Chords

First we will analyze the major chords in the progression (C and G).

A major chord is diatonic to three different major keys. Any given major chord can function as:

The I chord in a major key.
The IV chord in another major key.
The V chord in another major key.

If we use a note on the sixth string to represent the I chord:

The root note of the IV chord is located on the fifth string, on the same fret.
The root note of the V chord is located on the fifth string, two frets higher than the root of the IV chord.

The diagram in fig.2 shows the relationships between the root notes of the I, IV and V chords.

Fig.2

C Major Chord

A C major chord can function as the I chord in the key of C major.

To determine which key C functions as the IV chord in:

Locate the C on the fifth string, third fret (fig.3, highlighted in blue).
Locate the root note of the I chord on the sixth string, third fret — G (fig.3, highlighted in red).

C can function as the IV chord in the key of G major.

Fig.3

To determine which key C functions as the V chord in:

Locate the C on the fifth string, third fret (fig.4, highlighted in blue).
Locate the root note of the I chord on the sixth string, first fret — F (fig.4, highlighted in red).

C can function as the V chord in the key of F major.

Fig.4

So a C major chord can function as:

The I chord in the key of C major.
The IV chord in the key of G major.
The V chord in the key of F major.

G Major Chord

A G major chord can function as the I chord in the key of G major.

To determine which key G functions as the IV chord in:

Locate the G on the fifth string, 10th fret (fig.5, highlighted in blue).
Locate the root note of the I chord on the sixth string, 10th fret — D (fig.5, highlighted in red).

G can function as the IV chord in the key of D major.

Fig.5

To determine which key G functions as the V chord in:

Locate the G on the fifth string, 10th fret (fig.6, highlighted in blue).
Locate the root note of the I chord on the sixth string, eighth fret — C (fig.6, highlighted in red).

G can function as the V chord in the key of C major.

Fig.6

So a G major chord can function as:

The I chord in the key of G major.
The IV chord in the key of D major.
The V chord in the key of C major.

Minor Chords

Next we will analyze the minor chords in the progression (Am and Dm).

A minor chord is diatonic to three different major keys. Any given minor chord can function as:

The ii chord in a major key.
The iii chord in another major key.
The vi chord in another major key.

If we use a note on the sixth string to represent the I chord:

The root note of the ii chord is located on the same string, two frets higher.
The root note of the iii chord is located on the same string four frets higher.
The root note of the vi chord is located on the same string, three frets lower.

The diagram in fig.7 shows the relationships between the root notes of the I, ii, iii and vi chords.

Fig.7

Am Chord

To determine which key Am functions as the ii chord in:

Locate the A on the sixth string, fifth fret (fig.8, highlighted in blue).
Locate the root note of the I chord on the sixth string, third fret — G (fig.8, highlighted in red).

Am can function as the ii chord in the key of G major.

Fig.8

To determine which key Am functions as the iii chord in:

Locate the A on the sixth string, fifth fret (fig.9, highlighted in blue).
Locate the root note of the I chord on the sixth string, first fret — F (fig.9, highlighted in red).

Am can function as the iii chord in the key of F major.

Fig.9

To determine which key Am functions as the vi chord in:

Locate the A on the sixth string, fifth fret (fig.10, highlighted in blue).
Locate the root note of the I chord on the sixth string, eighth fret — C (fig.10, highlighted in red).

Am can function as the vi chord in the key of C major.

Fig.10

So an Am chord can function as:

The ii chord in the key of G major.
The iii chord in the key of F major.
The vi chord in the key of C major.

Dm Chord

To determine which key Dm functions as the ii chord in:

Locate the D on the sixth string, 10th fret (fig.11, highlighted in blue).
Locate the root note of the I chord on the sixth string, eighth fret — C (fig.11, highlighted in red).

Dm can function as the ii chord in the key of C major.

Fig.11

To determine which key Dm functions as the iii chord in:

Locate the D on the sixth string, 10th fret (fig.12, highlighted in blue).
Locate the root note of the I chord on the sixth string, sixth fret — Bb (fig.12, highlighted in red).

Dm can function as the iii chord in the key of Bb major.

Fig.12

To determine which key Dm functions as the vi chord in:

Locate the D on the sixth string, 10th fret (fig.13, highlighted in blue).
Locate the root note of the I chord on the sixth string, 13th fret — F (fig.13, highlighted in red).

Dm can function as the vi chord in the key of F major.

Fig.13

So a Dm chord can function as:

The ii chord in the key of C major.
The iii chord in the key of Bb major.
The vi chord in the key of F major.

Analysis

Our analysis tells us that each of the four chords in the progression is diatonic to the key of C major, the common key.

So we can use a C major scale to solo over the progression.

In the key of C major:

C is the I chord.
Am is the vi chord.
Dm is the ii chord.
G is the V chord.

The progression shown in fig.2 is reprinted in fig.14 with Roman numeral analysis.

Fig.14