Basic Types of Modulations

Direct Modulation

When a passage changes key abruptly with no commonly functioning chords or pitches, it is referred to as a direct modulation. This type of modulation is often used to create a sudden change of mood via it's sudden change of tonality.

[Modulation]

Common Chord/Pivot Chord Modulation

By preceding a modulation with a harmony that functions both in the old and new keys, the change of tonic becomes smoother and less abrupt. A chord that functions in both keys and is the chord immediately before the point of modulation is called a pivot chord. (Some theorists refer to this as a common chord. Either term is acceptable.) Pivot chords are identified by using roman numerals in both keys (one above the other), and a separating line or box to highlight their dual function, as in the following example. One of the previous examples used a pivot chord to smoothly modulate from Bb to gm. Notice how the vi chord in Bb is also the i chord in gm. By using a common pivot chord, our ears may hear the passage as functioning in g minor before the actual point of modulation.

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Pivot chords may be found by listing all of the chords in both the old and new keys, rotating the second key's chords so that the same letter names/roots are next to each other. Then identify chords that have both the same root and the same chord quality. Both of these must be the same for a chord to serve as a pivot chord.

For example, let us say we wish to smoothly modulate from D Major to E Major. First, list all of the chords and identify the common chords:

[Chart of Pivot Chords]
As we see above, we could use an f# minor chord (iii in D Major) or an A Major chord (V in D Major) as a pivot chord. The following two progressions demonstrate how each of these chords could function in this manner:

f#m pivot (iii)
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A Major (V) pivot
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Pivot Tone Modulations

In works that are not in a chorale style, composers often modulate through the use of a common tone in the melody. By eliminating the harmony, and only sustaining or repeating a pitch that exists in both the old and new keys, the music may smoothly modulate. This technique is frequently found in solo piano and chamber works of the common practice period.

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Closely Related and Distant keys

Keys that differ by only a single accidental (i.e. D Major with 2 sharps, and f# minor with 3 sharps) are referred to as closely related keys. Because of their similar key signatures, closely related keys contain multiple pivot chords, including the tonic in each key. This makes a smooth change of key easier for both composers and listeners. Closely related keys are easy to identify using the circle of fifths chart:

[Closely Related Keys]

All of the keys (both major and minor) that are adjacent a selected key are considered closely related. Notice also that the closely related keys also form all of the non-diminished, diatonic chords in the original key (be sure to use the natural minor scale form for minor keys). Hence, these new tonic's are familiar to the ear, making modulations smoother and more natural sounding.


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