key change
A shift from one key to another within a song or piece, also called modulation.
In Depth
A key change (or modulation) shifts the entire tonal centre of a piece to a new key. This can be subtle (a smooth pivot to a closely related key) or dramatic (an abrupt shift to a distant key). In pop music, the truck driver's modulation — a sudden shift up by a semitone or whole tone, often in the final chorus — is the most common type. Key changes add energy, freshness, and emotional impact. Moving to a higher key creates a sense of lift and excitement, which is why pop songs often modulate up for the last chorus. In classical music, modulation is a fundamental structural tool — sonata form is built on the tension between the home key and a contrasting key.
Beyoncé's Love on Top modulates upward FOUR times in the final section — each key change ratchets the energy higher, creating one of the most exhilarating endings in modern pop.