What does "tempo" measure in music?

"Tempo" in music refers specifically to the speed at which a piece of music is performed. It is measured in beats per minute (BPM) and dictates how fast or slow the music flows. This affects the overall feel and energy of a composition. For example, a fast tempo can create a sense of excitement or urgency, while a slow tempo might evoke a more relaxed or calm atmosphere.

In contrast, the other options pertain to different musical concepts. The emotional quality described in the first choice relates to the mood or feeling conveyed through musical elements and interpretation, which is distinct from tempo. Volume, the second option, deals with how loud or soft the music is played, independent of its speed. The duration of notes, as mentioned in the last option, concerns how long each note is held, which is separate from the rate at which a piece is executed. Each of these concepts plays a vital role in music, but they address different aspects from tempo, which is fundamentally about speed.