Opening narration is a storytelling or literature device, typically in the form of a monologue, by which background information about plot or characters is revealed so audience members can understand the rest of the story. This device is used in theater and film; it used to be common in radio programming as well. In some cases, lines from opening narration have become famous, epitomizing the entire story and even becoming synonymous with elements of the genre in which the story is held.
The length of an opening narration is not limited, but typically it is fairly short because it is intended only to set up the rest of the story. It is not unusual for these types of narrations to last a minute or less. The shorter the story, the less opening narrative there usually is. In the instance that the device is recapping previous episodes or installments, the narrative might have to be slightly longer than usual.
In addition to providing background information, opening narration is important because it sets the overall tone of the show. For example, if an opening narrative is full of puns or jokes or situational humor, the audience likely would expect the rest of the program to be comedic in nature. The opening narration must be able to fade seamlessly into the first true scene of the show. If it does not, the opening narration can make the viewer feel disconnected and confused.
An opening narration traditionally is one of the first things a person hears in the story. It often is within the initial scene of a play or movie. Sometimes a director opts to include a basic opening narration within the opening credits, however. Another alternative is to include the narration over the top of or along with the opening theme or overture. Two famous examples include the narrative from the television shows "Quantum Leap" and the original "Star Trek."
The fact that opening narration has to set the tone and provide information means that script writers pay close attention to how they craft the narrative. They know that audience members will lose interest quickly if the opening narrative does not have the right pace, feeling or information. Sometimes the opening narrative is the last thing a script writer creates because the writer has a better sense of how to introduce or summarize the story content when everything else is finished. It is not as common for writers to work in the opposite direction, using the opening narration as the basis for the rest of the script, but it really depends on the writer's creative process. If writers and producers feel the sequence no longer works for the show, they might rework it from season to season, especially if the narration is intertwined with the opening theme.