Modulation

Modulation is the process by which music changes key — moving from one tonal center to another. The technique is fundamental to tonal music: most pieces of any length modulate at least once, and complex works may modulate through many keys before returning to the home key.

Close modulations move to closely related keys (the dominant, the relative major or minor). Distant modulations move to remote keys. Each modulation creates a particular dramatic effect — close modulations feel natural and continuous; distant modulations feel surprising and dramatic.

The technique is essential to sonata form, where the second theme group typically appears in a related key (dominant in major, relative major in minor). The eventual return to the home key in the recapitulation provides structural resolution. Understanding modulation is essential to understanding tonal form.

Latin modulatio, from modulari (‘to measure, regulate’).

Mark modulations clearly. The harmonic shift to a new key should be audible — emphasize the new tonic, project the new key’s character. Modulations are dramatic events.