How are dynamics defined in music?

Dynamics in music are defined as the gradations of intensity of sound. This refers to how loud or soft a piece of music is played, which can greatly influence the emotional impact and overall expression of a performance. Dynamics are indicated in sheet music through various symbols, such as 'p' for piano (soft), 'f' for forte (loud), and other markings that denote changes in volume throughout the piece. Understanding dynamics allows musicians to communicate more effectively and add depth to their interpretation of the music.

The other options touch on different aspects of music but do not accurately represent the concept of dynamics. Variations in tempo relate to the speed at which music is performed. Specific key signatures refer to the collection of sharps or flats that define the tonal center of a piece. Visual representations of musical notes pertain to notation and do not convey the idea of volume or intensity. Thus, the correct answer emphasizes the essential role of dynamics in enhancing musical expression.