What is the term for a gradual decrease or increase in the level of light or sound?

The term that describes a gradual decrease or increase in the level of light or sound is "fade." This concept is widely used in theatre and film to create dynamic transitions, helping to set the mood or signify changes in a scene. For instance, a fade-out can indicate the end of a scene, while a fade-in can suggest the beginning of a new one. This technique is effective in enhancing storytelling through visual and auditory cues, allowing the audience to experience shifts in atmosphere naturally.

The other terms, while they may imply change, do not specifically capture the essence of a gradual transition as effectively as "fade." "Drop" tends to suggest a sudden decrease rather than a gradual one, while "shift" generally refers to a change in position or direction without the nuance of gradual intensity. "Gradient" relates more to levels or varying degrees but is not typically used in the context of light and sound transitions. Thus, "fade" accurately conveys the slow change in intensity which is essential in theatrical presentations.