There are certain narrative techniques which are common across both the film noir and neo noir movements and these traits have not changed across history – one of he best examples of these techniques is the use of voice over by the main character , this is a trope within itself and it is similar to the archetypal characters that are used within the genre in the sense that they are expected as part of the genre. Voice overs are often used while the main character is speaking to another character and this gives us a unique insight into what the characters are actually thinking – for example , at the beginning of Blade runner , Bryant recruits Deckard to hunt down the rouge replicants and while Bryant is talking Deckard is holding a neutral expression and his interior monologue tells us that Deckard dislikes Bryant and this is not something that would have been immediately evident by just his facial expression alone.
Voice over is only one technique that is a hallmark of the style of film noir and it helps to create a casual tone and it makes the audience think that they personally know the protagonist. Additionally , the intimacy that is created between the main character and the audience serves to raise the stakes of the action due to the fact that a personal dialogue has been created between the main character and the audience , who come to like the main character because they are afforded a unique insight into the minds of the characters and their thoughts and feelings.
Sunset Boulevard (1950 , directed by Billy Wilder) is an example of film noir where voice over is used by the main character in order to give the audience context as to what is going on in the narrative.
The voice over technique also serves a symbolic purpose due to the fact that one of the main themes in film noir is the duplicity of individuals and this is literally reflected in the way that the voice over technique is used to create a disconnect between what the main characters thoughts and their words and actions and this helps to create a sense of moral ambiguity because the audience doesn’t know if the main characters are reliable narrators because the aforementioned disconnect between the characters thoughts and actions sows seeds of doubt in the minds of the audience because it creates uncertainty as to weather the protagonist is good or evil.