cold open
A vivid moment before any introduction, used to hook the audience.
actuality
A recorded clip of a real voice, such as an interview.
natural sound
Real sounds recorded on location ("nat sound").
music bed / sting
Quiet music under narration / a short musical burst marking a transition.
signposting
Telling the audience where the text is going.
technique rationale
A statement explaining why a technique suits the purpose and audience.