What does "modulation" refer to in music?

Modulation in music specifically refers to the process of changing from one key to another. This change can create a sense of contrast or development within a piece, often enhancing the emotional impact or maintaining the listener's interest. Modulation can occur through various methods, such as using pivot chords or direct modulation, and it is a fundamental technique in composition and improvisation that allows for expansion and exploration of musical ideas.

The other options refer to different concepts in music. Arranging music for different instruments pertains to orchestration, which is focused on how instruments interact, rather than changing keys. Transitioning between fast and slow tempos refers to tempo changes, which can affect the pace of the music but is unrelated to keys. Altering tone color during performance relates to timbre and expression, focusing on how different instrumental techniques can change the sound's quality rather than its pitch structure.