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Hayes Music

Bach chorales, lesson 6 of 8

Modulation

Most chorales visit at least one related key, usually the dominant or the relative minor. From C major that means G major or A minor. A chromatic note in the melody near a pause is the usual sign.

How Bach modulates

1. Pivot chord. Choose a chord that belongs to both keys. From the pivot onwards, label chords in the new key.

CorrectA minor is the pivot: vi in C major and ii in G major

2. Confirm the new key with ii or IV, then V(7), then I of the new key.

Correctii, V7, I in G major: F#(A), the new leading note, rises to G

3. Return home with a note that cancels the new key. After a visit to G major in a C major chorale, an F natural does this, often as V7 or V4/2 of C.

CorrectF natural(A) turns G major into V7 of C, and the music is home

The whole journey together:

CorrectC major to G major and back

Labelling

Labels must match the key in force. A cadence onto G in C major with F# present is G: V to I, not C: V, as in the examples above.

In the new key the leading note changes. In G major the leading note is F#, so doubling F# is a doubled leading note, even though F# is not in C major at all.

Checking your work after a modulation

  • Does every chord after the pivot use the new key's accidentals?
  • Is the new leading note handled correctly (not doubled, rising to the tonic in the outer parts)?
  • Is the cadence in the new key in root position?