Which term signifies that the performer has freedom in their interpretation?

The term "ad libitum" signifies that the performer has the freedom to interpret the music in a way they choose. It indicates that certain parts of the music can be played at the discretion of the performer, allowing for personal expression and embellishment. This freedom can manifest in various forms, such as altering the tempo, adding ornaments, or improvising during specific sections.

In contrast, the other terms listed refer to specific characteristics of a piece rather than performer autonomy. "Allegretto" indicates a moderately fast tempo, while "agitato" describes a restless or agitated manner of performance. "Andante" suggests a moderately slow tempo. These terms set the framework for how a piece should be played but do not grant the same level of interpretive freedom as "ad libitum" does.