What does the term "ad libitum" mean in musical context?

The term "ad libitum" specifically means "at choice" in a musical context, allowing performers the freedom to interpret a passage in a way that suits them best. This could manifest as varying the tempo, dynamics, or even omitting certain notes or sections based on the performer's discretion. The flexibility afforded by "ad libitum" encourages artistic expression, enabling musicians to make personal choices that enhance the performance.

The other options present definitions that are more rigid in their requirements. A refers to a specific tempo, which contrasts with the liberating essence of "ad libitum." C describes a manner of playing that is both slow and expressive, but does not capture the freedom implied by "at choice." D discusses a gradual increase in tempo, which again is a structured approach that does not align with the idea of personal interpretative freedom indicated by "ad libitum."