Introduction to Modulation
By Raphael Crystal
It is sometimes necessary to move from one key to another in the course of a piece. This kind of harmonic motion is known as “modulation.” It should not be confused with transposition. While transposition involves taking a tune written in one key and playing it in another, modulation is the process by which you arrive at the new key.
Modulation is often useful when you are accompanying a singer or group of singers. Imagine you are accompanying the song, “My Country Tis Of Thee” in the key of F major. Our first example shows the last four bars of the tune:
For the last verse, to provide some variety, you might want to move to a new key. Typically, the move is up a half step. This doesn’t strain the singers’ ranges much, but it provides a bright, new sound. Here are the first four bars of the tune in the key of F sharp major:
The problem is how to get from the end of the tune in F major, as shown in our first example, to the beginning of the tune in F sharp major, as shown in the second example. This is an harmonic problem, which calls for an harmonic solution. The strongest, most direct harmonic movement is from a “dominant” chord (the chord built on the fifth degree of the scale) to a “tonic” chord (built on the first degree). This is known as a V-I progression. A dominant seventh chord may also be used, and this is called a V7-I progression.
To move from F major to F sharp major, we can use the dominant chord of the new key to point the way. Our next example shows the last two bars of “My Country ‘Tis Of Thee” in F major. After the final note, a C sharp chord has been inserted, which is the V chord of F sharp major. This establishes the new key, and the example concludes with the first two bars of the tune in F sharp major. The C sharp chord and the F sharp chord that begin the tune form a V-I progression. A little melodic phrase has also been added to guide the singers to the first note in the new key.
C#/C#E#C# to B (V)
C#/A# to G#
If, instead, we want to move up a whole step to the key of G major, we can use a D chord, which is the dominant in that key. Or, as in our next example, we can use a D7 chord so the progression is V7-I. Again a melodic phrase leads to the opening note. Notice that in both of our examples the modulation has been achieved without adding extra bars to the tune.
This is the neatest way to do it:
D/CDF# to G = D7 (V7)
D/A to F#
G/BDG = G (I)
We have been discussing the simplest form of modulation. In more complicated modulations a group of transitional chords may be involved, but almost always the dominant chord of the new key plays a major role.
If you would like to gain facility in modulation, you should become familiar with the V7-I progression in all keys. Our final example provides a pattern that can be extended up through all twelve tonalities. Practice it until it becomes automatic. When all of the dominants are (literally) at your fingertips, you will be ready to move the harmony in any direction.
GF/BDG = G7 to CE/GC = C
AbGb/CebAb = Ab7 to DbF/AbDb = Db
AG/C#EA = A7 to DF#/AD = D
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