CHAPTER 11 – COMMON-CHORD MODULATION

Modulation is a procedure that is constantly employed in tonal music. This topic introduces its principles, and describes the so called common-chord modulation, which is the most frequent of all types of modulation.

1. INTRODUCTION

- Modulation is defined as a change to another key with a certain permanence. In this respect, Modulation is not to be confused with Secondary Dominants, nor with Tonicization. The latter is only a brief change of key, of a temporary nature, and of very few bars in duration.

- Modulating implies that the ear adapts to a new tonic, and recognises it as such. In general, two circumstances must be present for this to happen:

1 - That you clearly hear, in the key of arrival, the notes containing accidentals different from those in the key of departure.

Im. 11-1

2 - That the progression V - I appears in the new key. If it happens several times, the better.

- Modulation is a useful device to provide harmonic variety to a piece. It involves a "change of colour" which, if done well, our ear will appreciate, as it generates interest and avoids the monotony of always remaining in the same key.

2. BASIC FORMS OF MODULATION

- Direct change of key: this is a change to a new key, directly and without any preparation. It usually occurs after a cadence. For instance, it is often used in pop music, when a verse is repeated one tone higher.

- V+7 - I progression in the new key: this kills two birds with one stone. On the one hand, the two chords gather together almost all the notes of the arrival key, so that the new accidentals are heard. On the other hand, we hear the progression V - I. In this way, we are able to adapt our ear to the new key at once. However, this is an abrupt procedure if there is no previous preparation, and especially if the keys have very different accidentals.

3. COMMON-CHORD MODULATION

- In Classical tonal music, composers have sought to make the modulation as smooth as possible for the ear, fooling it and leading it from one key to the next almost without noticing it.

- To achieve this, the technique is almost always the same: to use one or several common chords shared between the two keys, which act as a bridge between them. Let's see the procedure with an example.

- The common chords between the keys of F and C are the following (they have to be absolutely common, accidentals included):

Im. 11-3a

- Knowing these common chords, we can establish the following modulatory strategy:

Im. 11-3b

Given the example, we can compose a common-chord modulation according to the following steps:

1 - Study which common chords are shared by the two keys.

2 - Design a common zone, with one or more common chords (the more the better), which respects the harmonic logic, if possible, in both keys, but especially in the arrival key.

3 - Confirm the new key as soon as possible with a V - I progression.

4 - Make sure that the accidentals of the new key are heard, also as soon as possible.

5 - Reaffirm the new tonality with new V - I progressions. If the cadential 6/4 is included, the reaffirmation is particularly strong.

- And, we add a few considerations:

- As the aim is to deceive the ear, the smoother the linking of the chords is in the common area, the better.

- Some chords that are not normally used in the Basic Harmonic System of tonal music are nevertheless used as a common chord (mostly of the initial key):

- The III degree.

- The V and VII degrees of the minor mode without the raised seventh note of the scale.

- Until the new key is well established, it is preferable not to use secondary dominants, as they can obscure the modulatory process.

4. THE CIRCLE OF FIFTHS. MODULATION TO REMOTE KEYS.

- The following graph, in which the 24 different keys of tonal music are arranged in a circle, is known as the Circle of Fifths. The order of the circle is established according to the number of accidentals in the key signature.

- The Circle of Fifths is quite useful to know the number of common chords that we will find between two keys, and also to plan modulations to distant keys (with many different accidentals). Let's take a closer look:

- 1 Step in the Circle (e.g. C - G): 2 common chords, at least.

- 2 Steps in the Circle (e.g. F - Em): 1 common chord, at least.

- With 3 steps, there is no longer any guarantee of finding common chords. Only one will appear, in a very specific case.

- With 4 steps or more, there is certainly no common chord.

- What does this mean? The answer is that it is possible to modulate easily to keys up to 2 steps away in the Circle of Fifths. Beyond that, it is no longer possible. So, if we wanted to modulate to a key which is 4 steps away in the Circle, the only way to do it by common chords would be in two stages, using an intermediate key. For example:

Eb major => D minor (intermediate key) => G major

5. SUGGESTED EXERCISES.

- Harmonize the following soprano lines, performing the indicated modulations:

  8. Write a harmonic structure with the following features:

- Start in C major and end in A major, passing through an intermediate key.

- Make a perfect cadence in the intermediate key.

- Time signature: 4/4

  9.  Write a harmonic structure with the following features:

- Key: G major, Time signature: 4/4

- Form: 3 phrases of 8 measures (24 measures in total):

- 1st phrase: it modulates to D at the end of the phrase, closing with a perfect cadence.

- 2nd phrase: it starts in Dm (changing directly the mode), it modulates to Am and then to G, closing with a half cadence.

- 3rd phrase: it stays in G, closing with a half cadence.

- Harmonic rhythm: half notes, with an acceleration before the cadences. If necessary, it may also be accelerated in the 2nd phrase in order to complete the requested modulations.

- Add a free melody, which is structured in a motivic way. Aim for similarity in the 1st and 3rd phrases.