Before we get started, a small prerequisite to mastering modulation is a firm understanding of the relationship between keys. There's a great little tool for this that you've probably come across before - The Circle of Fifths.
As you may know, moving clockwise around the circle of fifths starting from C major, each successive key adds one sharp to the key signature. So for instance, C major has no sharps or flats, then moving on to G major, we add one sharp to the key signature. Or, moving anti-clockwise from C, one flat is added to the key signature. In essence, what this tells us is that only one note is different from any two adjacent keys.
And why is this useful? Well basically, by assessing the distance between two keys on the circle of fifths, we can determine how "closely related" they are. The more notes they share in common, the closer related they are, and vice-versa. This is useful to know when modulating, because a modulation between two very distant keys can sound very abrupt, compared to that of one between two closely related keys.
With the above in mind, let's take a look at some types of modulation and their uses.
Direct ModulationDirect modulation is the easiest to grasp in concept, but one of the harder methods to apply in practice. Direct modulation is also commonly called "Phrase Modulation," as this type of modulation succeeds a cadence at the end of the first chord progression's phrase. Direct modulation is very definitive, and often causes an abrupt sound, making it obvious to the listener that a key change has occurred.
This has been done countless times in pop songs, often where the last chorus is repeated a half tone or whole tone above the previous chorus, creating a lifting (although often cliché) effect.
Let's take an example of a direct modulation, from the key of C major to Db major. Remember, by studying the circle of fifths we can deduce that these two keys are very distantly related. Therefore we can expect the modulation to be easily apparent.
As you can see, as one phrase ends, the other begins, with no such transition to smooth over the modulation process. For a smoother change, however, we could use a different method for modulation:
C – F – G – C – Db – Gb – Ab – Db
I – IV – V – I – I – IV – V – I
|-----Phrase 1----||-----Phrase 2----|
Pivot Chord ModulationAlso called "Common Chord" modulation, this is the process of transitioning between two keys through the use of a common chord. You'll find that this won't work for keys that are too distant, as they do not actually share any common chords on which to "pivot" the tonal centre. To do this, we first need to establish the chords within the two keys so we can compare which belong to both. Let's take the keys of C Major and G Major.
C, Dm, Em, F, G, Am, Bdim, C
G, Am, Bm, C, D, Em, F#dim, G
From this we can deduce that the two keys share the following chords:
G, Am, C, Em
In theory then, we should be able to use any of these chords to pivot the progression to a new tonal centre. To do this, we place it between the two keys. Let's take Em as an example:
The above progression is actually rather ambiguous as to where the modulation takes place, as the first six chords actually all belong to the first key. This provides a very smooth transition that, as a listener, is hard to place. For a more definite Pivot Chord Modulation, you might want to use two keys that are more distantly related, using the circle of fifths.
C – F – G – Em – G – C – D – G
I – IV – V – I – I – IV – V – I
|--Key 1 (CMajor)--||--Key 2 (G Major)--|
Alternatively, using the above progression, an extension of G to Gmaj7 would highlight the key change, as the F# note in Gmaj7 does not belong to the original key of C major. And similarly, if you were to add a melody, you could select and place the "new" notes from the second key at the specific point you want the key change to become apparent.
Common ToneThe last type of modulation we're going to cover in this lesson is the "Common Tone" modulation. As you've probably guessed, instead of using a common chord, this type of modulation just uses one note to make the transition, allowing the movement to very distant keys.
Common Tone Modulation is most frequented by sustaining one note for a prolonged period of time, whilst the underlying chords change, thus altering the function of that note.
Let's attempt a modulation from C Major to Ab Major, starting by identifying the common notes:
C, D, E, F, G, A, B, C
Ab, Bb, C, Db, Eb, F, G, Ab
So the common notes shared by both keys are:
C, F, G
Let's use C, the root note of C Major, but the major third of A Major. The chords are written above the tab, which simply notates a sustaining C note. I'd recommend playing this along with another guitarist so you can hear the full effect, or possibly on a keyboard, where you can easily change the chord underneath the same note.
I suggest whilst experimenting with this last method that you think about how you'd like the note to function in both keys. For example, holding a G note instead of a C would create a different effect, as it would function as the seventh over the Ab chord.
C (let ring) Ab
And there you have it - the 3 most commonly used methods for modulation. Play around with them and most importantly try to implement them within your writing!
About the Author:
Sam Dawson is a singer/songwriter who specializes in fingerstyle and percussive guitar. For more songwriting tips, sign up to his free songwriting email course.