Part III

Modulations to the Dominant Key

modulations

In most Common Practice Period music, the music rarely stays only in the given key signature, but changes key, or modulates from the tonic key to other ones that are closely related to it.

Probably the most common modulation for major key pieces is from the tonic key to that of its dominant. Two examples are shown above.

When planning modulations, it can be useful to imagine that we are joining two chord progessions, each of which is in a different key, with the intention of creating a larger musical structure. One possibile technique is to join the two progressions by having them overlap by a single chord.

The chord used in the join is called a pivot chord. Its main quality, the glue to hold our join, is that the chord must be found in both keys. Another way of describing the pivot chord is to say that it is common to both keys. The chosen chord should also be easily used as a pre-dominant chord in the new key.

In the first example, we chose the triad CEG, as our pivot chord in our modulaton from C major to G major. The reason why it works is twofold:

  1. CEG is common to both C major and G major: I in C major, and IV in G major
  2. As a IV chord in G major, it can easily lead to V

A similar situation is shown in Ex. 2. The triad chosen as our pivot chord is ACE. This triad is vi in C major, and ii in G major. In its second interpretation, the triad easily moves to V in the new key.

Study the above two progressions and the chordal analysis used carefully. Try the chord progessions in different keys to get a feel for how these modulations work.

Modulations are introduced in Grade 3 Harmony, but become a major part of the material of Grade 4 Harmony. Mastering modulations to the dominant key will help establish a basis for later work in harmony.