What term is used to describe a gradual increase in volume in music?

The term that describes a gradual increase in volume in music is "crescendo." This musical directive indicates that the performer should gradually play louder, building intensity and often creating an emotional effect as the music develops. Crescendo is an essential dynamic marking in compositions, as it guides musicians on how to shape phrases and convey the intended expression.

The other terms do not describe a gradual increase in volume. For instance, "diminuendo" refers to a gradual decrease in volume, providing the opposite effect of a crescendo. Terms like "pianissimo" and "mezzo forte" indicate specific volume levels—very soft and moderately loud, respectively—rather than a dynamic change over time. Understanding these terms is crucial for interpreting and performing music accurately.