In music, what does the term 'modulation' primarily indicate?

The term 'modulation' in music specifically refers to the process of shifting from one key to another. This technique is often used to create contrast, build tension, or add interest throughout a piece of music. Modulation can be achieved through various methods, such as pivot chords, direct modulation, or using key sequences, and is a fundamental element in the structure and emotional development of compositions.

When a piece modulates, it can evoke different atmospheres or feelings, enhancing the expressive quality of the music. This transition between keys can occur anywhere in a composition, leading to shifts in tonal center that engage the listener and provide a sense of progression. In contrast to the other options, modulation specifically emphasizes the change in tonality rather than the repetition of melody, changes in tempo, or the maintenance of a single key throughout a piece.