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Modulation in music: what it is, what it is used for

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Modulation is a movement of chords by which a piece of music changes from one key to another. Modulation is most often used in the classical and jazz repertoire, while it is used less in rock and pop, where songs usually remain in the initial key throughout their entire duration.

Il concetto di tonalità e di modulazione

Almost all pieces of music choose a reference scale, from which the notes of the melody and the chords for the harmony are derived. The concept of tonality therefore concerns both scales and chords.

In a dedicated lesson we have already explained the relationship between scale and chord and how chords are in fact derived from a scale. If a piece of music is composed in the key of C major, this means that its melody is predominantly built on notes from the C major scale, and that most of the chords are derived from the same scale.

In the tonal music system there are 12 major and 12 minor keys. The choice of tonality is therefore limited to these twenty-four possibilities.

How does the composer choose the key?

The tonalities are all the same, or at least very similar. The difference between one tonality and another is mainly of register, i.e. one tonality can be more or less high/low than another.

For example, the key of C# is a semitone above than the key of C, so it is a little higher. The key of B major, on the other hand, is a semitone below C, so it is in a lower register.

Here are some examples. I will now play the C major scale, and after a short break the C# major scale. You can hear that the second scale is slightly higher than the first.

I will now play the C major scale, and after a short break the B major scale. You can hear that the second scale is slightly lower than the first.

Since scales are very similar to each other, the composer takes three aspects into account when choosing the key of a piece. We will consider them one by one.

1. The singer's vocal register

Some keys are more suitable for male and some for female voices, and each singer has his or her own preferred register. If a piece is to be performed by a given singer, the choice of key will be largely determined by his or her vocal register.

2.The register of musical instruments

There are some instruments that have a very wide range, such as the piano or guitar. Other instruments, such as wind instruments, have a more limited register and therefore sound better in certain keys.

Also from a technical point of view, each instrument has tonalities that are more or less easy to play, depending on the position of the hands. If a musical composition is created for a certain group of instruments, the composer can easily choose the key with these practical aspects and ease of performance in mind.

3. The typical nuances of each key

Each key has its own specific timbral nuance, determined by the register but also by aspects that cannot be measured or explained. Perhaps some tonalities sound more interesting because they have been less used in the past, but there is something that distinguishes them and makes each tonality unique, especially to the experienced ear of a composer. A capable composer knows these nuances and uses them to make a piece of music more interesting.

Now that we have clarified the concept of tonality, we can explain what modulation is, i.e. the transition from one tonality to another.

Modulation

Every piece of music has a starting key, which in some cases remains unchanged throughout the piece. In other cases, the composer uses more than one key within the same piece of music to provide more variety. In order to switch from one key to another, a process called modulation is used.

The change of key or modulation may have practical reasons related to the instruments or singers used in the performance, but more often it has aesthetic reasons. Modulation is necessary to make the piece more interesting and varied.

The longer and more complex a piece of music is, the more necessary one or more modulations will be in the piece. It is common for a three-minute song to employ only one key and thus not contain any modulation, whereas an orchestral piece, e.g. a symphony or an overture, certainly moves between different keys and thus makes extensive use of modulation.

Close and distant keys

Modulation is a process that does not always take place in the same way. In particular, it is very important how close or distant two tonalities are. They are close if they have many notes in common, and distant if they have few notes in common.

In the diagram called the circle of fifths, the closest keys occupy adjacent positions on the perimeter of the circle. For example, C major is close to F major and G major, but it is distant from E major.

modulation and circle of fifths
The circle of fifths

Modulation with and without preparation

Modulation between two close keys is relatively easy, and is most common in simple, easy listening pieces. Modulation between distant keys, on the other hand, is more complicated and requires a series of intermediate, or transitional, chords. These chords serve to prepare the modulation itself and to make it less sudden and unpleasant.

The preparation of the modulation is that phase in which the piece moves from the common chords between the two keys to chords specific to the new key. Normally the modulation is considered to be completed when the characteristic chords of the new scale are clearly stated. That is, the chords of the fourth, fifth and first degrees.

Chords used for modulation

The most commonly used chord for modulation is the dominant chord, i.e. the seventh chord built on the fifth degree of the scale. Often, modulation takes place through the perfect cadence II V I.

For example, if I'm moving from the key of C major to F major, I'll use the II V I chords of F major: Gm7 C7 F. Now let's look at a series of modulations in the jazz piece Tune Up.

Tune Up modulates repeatedly, descending by tone using a series of II V I passages:

  • Em7 A7 D for the initial key D (yellow)
  • Dm7 G7 Cmaj7 for the key of C (in orange)
  • Cm7 F7 Bbmaj7 for the key of Bb (in purple)
Modulations in Tune up
Modulations in Tune up

Another jazz piece that features numerous modulations is All The Things You Are. In addition, jazz pieces with the AABA form often modulate to a different key in the B part. For example, Take the A Train and Body and Soul, two classic jazz standards, follow this pattern.

Diminished chord as passing chord

A chord that is particularly used for modulation between two distant keys is the diminished chord, which is marked with dim7. The dim7 chord is very unique in that it is formed by symmetrical intervals and is the only seventh chord to have this characteristic.

Precisely because of this symmetry, the dim7 chord belongs to several keys simultaneously. This peculiarity makes it an ideal tool for modulation. When a composer "brings" the piece of music to a diminished chord, multiple modulation possibilities open up.

As an example, the diminished chord is widely used in the opera repertoire, where modulations are indispensable. In an opera, there are several singers, each with their own vocal register. When the word (or rather, the singing) passes from one to the other, it is often necessary to change tonality. The diminished chord is one of the most frequently used solutions.

Would you like to learn more about these concepts?

If these concepts are too advanced for you, you may be interested in the functional harmony course available on this website.

Most common modulations

We have said that a piece of music can modulate to any key, close or distant. However, there are some particularly common modulations:

  • Modulation to relative tonality
  • Modulation to parallel tonality
  • Upward modulation by semitone or tone
  • Back-and-forth modulation between two keys

Modulation to the relative key.

The most frequent modulation is that between a key and its major or minor relative. In fact, every major key corresponds to a relative minor, and every minor key to a relative major. The two relative keys share the same alterations in the key signature and are therefore implicit in each other.

An example of this type of modulation is the jazz piece entitled Fly Me to The Moon, which switches from the major to the relative minor key, and vice versa. The transition from major to relative minor is extremely smooth and natural, so much so that we do not notice the precise point at which we have switched from one to the other.

Modulations in Fly Me to the Moon
Modulations in Fly Me to the Moon

In the score above, the II V I passages on the C major scale are highlighted in yellow, and the II V I passages on the relative A minor scale are highlighted in pink.

Modulation to parallel key

Another rather common type of modulation is that between a major key and its parallel minor key, or vice versa. While relative keys are built on different notes, e.g. C and A, parallel keys are those built on the same starting note. For example, C major and C minor.

Two parallel tonalities are not close tonalities, they have three alterations of difference. However, they have a very strong link, since both scales start with the same note.

The transition between a major mode and the parallel minor (or vice versa) is therefore well accepted by our ear. Let us listen to an example, a song by Fabrizio De Andrè entitled La ballata del Miché. The song is a traditional Italian valzer.

This is the series of modulations La ballata del Miché.

  • 0'47'' change from A minor to A major
  • 1'28'' modulation from A major to A minor
  • 2'00'' again from A minor to A major

Upward modulation by semitone

Bobby Hebb's classic soul song Sunny modulates repeatedly by going up a semitone. Going up just one semitone is a change within the reach of any singer, as the variation is modest. However, the modulation creates more tension and makes the piece more interesting. In this case, for example, the song is based on a verse of only 16 measures that always repeat the same. Without these modulations, the piece would probably be more boring and repetitive.

Sunny parte in tonalità di Em, ecco la serie di modulazioni:

  • 1'02'' From Em to Fm
  • 1'31'' From Fm to F#m
  • 2'01'' From F#m to Gm

A couple of Italian songs that modulate by going up a semitone in the same way are Grande grande grande by Mina and 4 marzo 1943 by Lucio Dalla.

Upward tone modulation

In The Summer Wind, an American classic sung by Frank Sinatra, we find a modulation that occurs by going up one tone. The song starts in Db and goes up twice, thus reaching the tones of Eb and F.

Here is the series of modulations in The Summer Wind:

  • 1'05'' from Db to Eb
  • 1'48'' from Eb to F

Back and forth between two tonalities

In the cases we have considered so far, modulation occurs by going up a semitone or tone, without ever going back. Let's now look at a piece in which modulation occurs between two tonalities, at intervals of a minor third. The two keys alternate repeatedly.

Fabrizio De Andrè often used this expedient in his songs. See for example La canzone di Marinella, which begins in the key of A minor, modulates to Cm, then returns to Am, and so on.

Here is the series of modulations of La canzone di Marinella

  • 0'53'' from Am to Cm
  • 1'18'' from Cm to Am
  • 2'06'' from Am to Cm
  • 2'30'' from Cm to Am

La Canzone di Marinella is undoubtedly a literary masterpiece, but the music is very simple and predictable. In order not to repeat the same melody so many times, always the same, De André cleverly alternates the two keys. Thanks to the repeated modulations, the song becomes more interesting and varied.

The same harmonic solution can be found in other songs by Fabrizio de Andrè, e.g. La città vecchia, Bocca di Rosa, Preghiera in gennaio

An unusual case: modulation by fourths

Finally, let's look at a rather unusual situation, Stevie Wonder's Evil. The song modulates as it goes up in pitch, but with much larger jumps than Sunny (which went up a semitone each time) and The Summer Wind (which went up a tone).

Evil starts in the key of C major, and three times it goes up a fourth. We can see the difference from semitone or tone jumps: here the transition is much stronger. Through these wide leaps, Stevie Wonder moves into an increasingly higher register. By the end of the song, he will have sung in the full two octaves. Not bad at all!

Evil - Stwvie Wonder
The first 12 bars of Evil

Above are the chords of the first verse, in C major. The passage is repeated exactly the same in the new keys, by modulating in this way:

  • 1'30'' from C to F
  • 2'08'' from F to Bb
  • 2'45'' from Bb to Eb

Here the key changes are then used to show off the singer's great vocal qualities.

Conclusione – riconoscere la modulazione

In this lesson we have looked at the simplest modulations, those that we can easily identify within a song. For those who want to play modern repertoire, pop or jazz, being able to recognise a modulation on the fly is essential. I hope I have managed to explain clearly what a modulation is in music. If you have any questions, or would like to give us your opinion on the lesson, please write in the comments to the article. Thank you!

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