Modulation

In music, modulation is the process of changing from one key (tonal center) to another. If a piece of music starts out in the key of F major but then changes, either immediately or gradually, to the key of Bb major, we would say it modulates from F major to Bb major. A piece of music is considered to be in a "key" provided the root of the key is the tonic, also called "home" or the "gravitational center".

In some definitions, a modulation is not considered to have taken place until the new key has been confirmed with a perfect authentic cadence. More loosely though, you have changed key if a new tonal center feels now like the tonic.

This is the process that pieces of music go through to change the tonal centre from one key note to another. For example, a piece may modulate from Key C major to Key G major so that Key G takes over (albeit temporarily) from Key C as the keynote.

Modulation is central to compositional approach or technique in classical music but to a lesser extent in modern popular music. Much has been written in composition text books, harmony books and theoretical texts about modulation, probably because the process of key change is reasonably well understood as it is a consciously learned process for composers. This contradict the organisation of chord progressions into syntactic structures which is largely subconscious.

  

Why Modulation?

The question here is what is the purpose behind modulation in a piece of music or point for modulation?

One reason is to add interest and variety to our music. Especially if we repeat the same sections many times, changing the keys will, at the very least, give our listener something interesting to hear. The contrast of the first key with the second key, or an intensity increment or decrement, can be interesting even on a subtle level.

Modulations frequently provide a sense of forward propulsion and technically drive the music into new levels of energy. In the classical repertoire, a majority of musical pieces modulate to the key of the dominant, and the establishment of an extra sharp (for example introducing the pitch F# to modulate from C to G major) can give the music a lift and direction.

From a practical standpoint, a film composer might need to write a piece of music that fits between two already existing songs in different keys to create an effect that change the mode of the scene. In this act, the middle piece will need a smoothly transition from the key of the first piece to the key of the second. Or if there is no transition, the composer needs to at least be aware of the effect of a sudden change in key and make sure it is welcome.

 

Other purpose of modulation is to help give music structure, direction and create a define mode. Modulation can trigger a variety of emotional responses from the listener. Depending on the technique or amalgamation of techniques used, modulation can help music to more effectively evoke a mood. Modulation facilitate limitless harmonic and melodic variety while retaining unity. A successful modulation administer the brain with a new orientation of tones and chords, a leap into a musical parallel universe.

Act of Modulation

Modulation in a piece of music is often associated with the formal structure of a piece. A music piece in a major key often modulates to its dominant key and there is often a cadence in the dominant at the end of the first segment of the piece. For example, a piece starting in C major often ends its first section with a cadence in G major. The second section of a piece then takes the music back to the tonic key either directly or via other related keys.

Music pieces in the minor key usually move to a cadence in the relative major key at the end of the first section. For example, a musical piece in A-minor can possibly end its first section with a cadence in C major. The second section will then takes the piece back to the original tonic key.

The distance of the key change varies between eras or periods in musical history and from one composer to another composer. The length of the time used (stay) in each new key can also vary considerably from a brief stop off (sometimes referred to as transient modulation or tonicization) to a whole segment in a new key (sometimes referred to as transposition although this can also mean the transfer of a whole piece into a new key). Sometimes pieces can pass through several keys before settling on a new key center or returning to the home key.

 

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