Playing with Different Keys
-a lesson on modulation-
What is Modulation?
Simply put, modulation is a change of key found in the same musical piece. Modulation brings movement to music. Although many songs are built around a single key, you will most likely come across some chord progressions built around two or more keys.
Knowing how to approach these situations requires method and a good knowledge of theory. This guide should help you understand how to play and think while improvising over series of chords that cannot fit a single scale.
Basics of Improvisation
The first thing to do when facing a series of chords to improvise over is to group them into a common scale. Most players do that automatically by ear, but some simple rules apply. Several approaches can be taken, but we will discuss the most efficient in the following example.
Let's consider the following chords:
G - C - Am - D
Let's now extract all the notes found in each of the previous chords:
G = G - B - D
C = C - E - G
Am = A - C - E
D = D - F# - A
Let's now take all the notes we extracted and reorganize them in alphabetical order starting from the root of the first chord in our chord progression (G):
G - A - B - C - D - E - F#
In this particular case, we came up with a seven note scale made of seven different notes. The scale we came up with gives us the key of the song: G Ionian (commonly called G Major).
Before moving further, spend time analyzing the following chord progressions and figure out which key they are built upon. Each of them are built in a single key (no modulation). The answers can be found at the end of this guide.
Example 1
A - Bm - D - E
Example 2
Dm - G - C - Dm
Example 3
Gm - Ab - Fm - Ab
The Modulation Problem
When facing a chord progression that will include a modulation, the improviser will need to think fast to change keys in time. Let's try to come up with useful shortcuts that will help us in that task.
The following chord progression includes a modulation.
C - Am - F - G
D - Bm - G - A
Let's apply the method described in the previous section on the previous chords:
C = C - E - G
Am = A - C - E
F = F - A - C
G = G - B - D
D = D - F# - A
Bm = B - D - F#
G = G - B - D
A = A - C# - E
Let's now organize all the notes we extracted from the chords in alphabetical order staring from the root of the first chord (C):
C - C# - D - E - F - F# - G - A - B
As you can see, we get from this quite a large scale including the same note with different accidentals (for example C and C#). Whenever this happens, you can be sure that you are facing a key change.
Let's now organize our scale according to the chords and see where we can break our chord progression and switch keys. We will do this by paying close attention to the notes of the scale featuring accidentals. In this case we'll look for C - C# and F - F#.
The first chord includes the note C which is one of the notes that had a different accidental in the scale.
We find the C note throughout the first four chords. The fifth chord however includes a C#. That C# remains as it is until the end of the chord progression. That is a good indication that the key changes right on the fifth chord.
To make sure that the modulation happens in that place, we need to check where the altered F takes place. A quick look at the chord progression tells us that the first appearance of F# happens also on that first chord. That means that our chord progression modulates right on the fifth chord.
Let's now see which scales we can come up with according to the chords we have. The first scale will include C and F, the second will include C# and F#:
Scale used: C - D - E - F - G - A - B = C Ionian
C = C - E - G
Am = A - C - E
F = F - A - C
G = G - B - D
Scale used: D - E - F# - G - A - B - C# = D Ionian
D = D - F# - A
Bm = B - D - F#
G = G - B - D
A = A - C# - E
Following are a couple chord progressions that include a modulation. Using the same process discussed previously, try to write down the scales involved.
Example 4
G - C - F - G
A - D - G - A
Example 5
Bm - C - Am - C
Gm - Ab - Fm - Ab
Going Further
As always with musical concepts such as these, it is important to remember to keep your ideas musical. Always apply what you have learned on your instrument. Use the provided backing tracks on JamPlay to explore how these ideas sound on the guitar.
Keep your improvisation simple and melodic. Listen to the chord progression you are working with before playing over them and try to anticipate the key change. Focus on one area of the fretboard at a time and gradually expand your fretboard knowledge.
Practice well, don't get overwhelmed and keep it fun!
Answers to Exercises
Example 1
A Ionian = A - B - C# - D - E - F# - G#
A = A - C# - E
Bm = B - D - F#
D = D - F - A
E = E - G# - B
Example 2
D Dorian = D - E - F - G - A - B - C
Dm = D - F - A
G = G - B - D
C = C - E - G
Dm = D - F - A
Example 3
G Phrygian = G - Ab - Bb - C - D - Eb - F
Gm = G - Bb - D
Ab = Ab - C - Eb
Fm = F - Ab - C
Ab = Ab - C - Eb
Example 4
G Mixolydian = G - A - B - C - D - E - F
G = G - B - D
C = C - E - G
F = F - A - C
G = G - B - D
A Mixolydian = A - B - C# - D - E - F# - G
A = A - C# - E
D = D - F# - A
G = G - B - D
A = A - C# - E
Example 5
B Phrygian = B - C - D - E - F# - G - A
Bm = B - D - F#
C = C - E - G
Am = A - C - E
Bm = B - D - F#
G Phrygian = G - Ab - B - C - D - Eb - F
Gm = G - B - D
Ab = Ab - C - Eb
Fm = F - A - C
Ab = Ab - C - Eb