Which term refers to the speed at which a piece of music is played?

The correct term that refers to the speed at which a piece of music is played is "tempo." Tempo indicates how fast or slow the music is intended to be performed, often measured in beats per minute (BPM). Composers specify the tempo to guide musicians on how to interpret the feeling of the piece, influencing its emotional impact. For instance, a fast tempo can create a sense of excitement or urgency, while a slow tempo might convey calmness or introspection.

Other terms listed serve different functions in music: dynamics refers to the volume of sound, key relates to the tonal center or scale of the music, and texture describes the interplay of different musical lines or layers within a piece. Each of these aspects contributes to the overall understanding of a piece of music but does not pertain to its speed.