Which element of music relates to the arrangement of sounds in time?

The element of music that relates to the arrangement of sounds in time is rhythm. Rhythm encompasses the timing of notes and chords in relation to each other within a piece of music, establishing the pattern of sounds and silences. It dictates the pace and flow of the music and is crucial for creating the feel of a piece, whether it's a steady beat or a complex syncopation.

In contrast, harmony pertains to the combination of different musical notes played or sung simultaneously, creating chords and progressions. Melody involves a sequence of notes that are perceived as a single entity, often the main tune of a piece. Dynamics refer to the volume of music, indicating how loud or soft a sound should be played. Understanding rhythm is fundamental to grasping how music is structured over time, making it an essential element in musical composition and performance.