Music plays an important role in comedy movie trailers to make them seem more lively and humorous, though it is not as essential as in horror genres. The trailer for Ted uses different songs to match the tone of various scenes - a mystical song for his origin story, an upbeat friend song for scenes of them grown up, and a fast-paced song for an action scene. The document discusses how understanding how to apply the right music to different parts of a trailer can enhance the viewing experience.