modulation
The process of changing from one key to another within a piece.
In Depth
Modulation is the process of moving from one key to another within a piece of music. A well-crafted modulation uses pivot chords — chords that belong to both the old and new keys — to make the transition sound smooth and natural rather than abrupt.
Modulation is one of the most powerful tools in a composer's arsenal. It can create a sense of journey, heighten drama, or provide contrast between sections. Common modulations move to closely related keys (the dominant or relative minor), while more distant modulations create a striking effect. Schubert was a master of unexpected, magical modulations that shift the harmonic colour in an instant.
Schubert could modulate to remote keys so smoothly that listeners feel transported without knowing how they got there. His modulations in the late piano sonatas are considered among the most magical in all music.