What does "modulation" mean in music?

Modulation

Modulation is a fancy word for key change -- switching from one key to another in a single piece of music. It is a common practice in composition (both classical and rock or pop) and can be used to a variety of effects. Modulation can be subtle and smooth or abrupt and startling. It can cast an eerie glow on a piece of music or completely change the mood and direction. The effect achieved, however subtle or abrupt, is largely dependent on the type of modulation used.

The most common type of modulation is called pivot chord modulation. In this type of modulation, the key changes based on a chord shared by both keys; the destination chord often has the same root note or quality as the original chord. This allows for a smooth, almost foreshadowed modulation. A good example of this is found in the last chorus of rock songs; this type of modulation is used there to an almost triumphant effect.

Another common type of modulation is pivot tone modulation. Similar to pivot chord, pivot tone modulation uses a common pitch to move from key to key. This type of modulation is also subtle, depending on the piece of music in which it is used. It can, however, be used to a startling effect if the two keys have few notes in common. In songs using pivot tone modulation, the common pitch is often sustained or repeated and used a bridge between the two keys.

The most abrupt kind of modulation is direct modulation. The name is exactly what is says it is: a direct modulation using no common note or chord to bridge the two keys. When used correctly, direct modulation is shocking and can easily change the song's mood. This type of modulation switches keys either at a phrase's end (phrase modulation) or at a point in the middle of the song (static modulation).

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Transposing a song from one key to another

Transposition is changing the key of a piece of music, or changing the notes without changing their relationship.

This is often done to make the piece of music easier to play or sing. It's a common practice in bands that don't perform their own material; the singer may wish to cover a song with vocals that are far out of his or her range. Transposition can correct that problem by shifting the key into a range that is comfortable for him or her. Transposition is also used with instruments. Some instruments (called transposing instruments) are not tuned to the same note; for instance, a bass clarinet is tuned to a B flat and a high clarinet to an E flat. Transposition of the sheet music for these instruments ensures that they won't sound awkward and flat when playing with the rest of the orchestra or band.


Transposition by scale degree uses the scale degrees of a piece of music to determine the relationship between the notes. Each note in a piece is assigned a scale degree (tonic, submedian, etc.) and the same scale degrees are used for the new chord. This type of transposition is potentially simple, as the relationship between the notes will always remain the same, regardless of the key.

Transposition by harmonic interval uses intervals as a guide for the transposition. By finding the interval between the dominant notes in the two keys, one can deduce the interval between the all the notes. If the difference between the notes is a major third, then transposition of all the notes will be done by a major third. This type of transposition is also potentially simple but calls for an added carefulness when dealing with accidentals that aren't expressed in the key signature.

I personally use a combination of the two, but the real secret to transposition is to be able to think in each key; in other words, to be as fluent in one key as you are in another. Most people start out playing everything in the key of C, since the scale of C has no black keys. I have a friend that did just the opposite -- he played everything in the key of Gb, because that way he could use all the black keys and only a couple of the white keys.

In any case, get familiar with all 12 major keys and all 12 minor keys. That way you won't be in a "foreign country" when you need to play in some key you aren't used to. It's analagous to learning to speak 12 languages to some degree -- at least enough to get by.

And by the way, many people confuse transposing and modulating. Modulating is the process you use to get from key to key -- like a smooth hallway between keys.