Just to remember, we already know how to discover the tonality of a song. It is just to see its chords, because they show us which is the harmonic field in question and, therefore, they inform which scale we can use to improvise or do arrangements.
But many songs have more than one tonality, in other words, they change from one harmonic field to another. For example, let’s say that a song has the chords C, Em, F, G and Am. We could say that the tonality is C major. Imagine now that in the chorus the chords Bb, Gm and Dm appear. These chords belong to F major harmonic field, and not C major. In the chorus, the tonality of this song changed, so we can say that a “modulation” happened in this part. In the point of view of improvisation, we would use F major scale in the chorus, due to the fact that tonality there is F major.
Modulation and Transposition
Modulation can be short, which means that they last for a short time and then return to their original tonality; or they can stand for a long time, changing definitely the song’s tonality. When the song modulates and does not return to its initial tonality, we say that a transposition happened. This definition, though, it’s not universal; many musicians call any modulation by transposition and vice-versa. The main point is to understand that actually, modulation and transposition are the same thing: changing tonality.
There are many ways of doing modulation, and we will study this in advanced topics. Our target here is just to give you an introduction about the concept, because we will mention this word many times from now on.
As you saw, there is no mystery. Along our studies you will learn many resources and different ways of exploring this subject. To dominate styles that are more complicated like Jazz and Bossanova, this knowledge will be fundamental. Even if you want to play only basic songs (that normally doesn’t have modulation) this study is interesting. Knowledge is never too much, and when it comes in an easy way, it is better! Einstein said: “The mind that opens to a new idea never returns to its original size”. After a while studying here in the website, probably you will be able to listen and realize things that you couldn’t see before. This will increase your perception and your musical pleasure, undoubtedly.
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