Theatre shares close links with film; the audience is watching a framed area in which the audience is shown the ongoing action. Even when films were silent, they had musicians playing in the picture houses much like how a pit orchestra plays music for a play or musical. Similarly in cinema, the line between diegetic and nondiegetic music is blurred. Robynn J. Stilwell states an instance where the line blurs in theatre:
“The two may converge, for instance, in a ballroom scene, where the live music is pretending to be that of the musicians seen or presumed on screen, but the physical separation is plain to anyone in the audience” (Stilwell 2007:188).
In this example the audience chooses when to accept the musicians into the narrative and the reality of the story. The audience is never told to do so and yet makes the transition between the non-diegetic underscoring of the scenes to the diegetic music of the ballroom. Until the point of transition between diegetic and nondiegetic the audience is accepting of the fact in the reality of the show music is accompanying the action on screen with no source.
There are some other examinations of the term diegetic by Neumeyer who argues that it could be used to refer to the noises within the setting in which you are watching the movie (2009), for example, the sound of people laughing or eating popcorn. If we take this notion and situate it within the context of theatre it could be claimed that watching a recorded show does not give you the same experience as seeing the show in person. A current example of this debate is the American musical Hamilton (Miranda 2015) which was released on Disney+ in the summer of 2020. The filming of the musical took place over three days and was an amalgamation of two shows recorded with a live audience. In the recorded musical we can hear the crowd in the background clapping, laughing, and cheering. But why keep this ambient noise in since supposedly none of it adds to the narrative and may in fact detract from the action on stage? By making the swap over between the two mediums, we begin to lose the magic and emotion of the original piece. Sitting down in the theatre with the unspoken excitement and cacophony of programmes being flicked through all adds to the experience and blurs the line between what is part of the show and what isn’t.
Subsequently, in the context of theatre, Neumeyer's idea that diegesis could include the noise surrounding the audience in the theatre is a valid one. We could link this back to the experiences of the silent era of film where the picture house/cinema you went to had different live music playing making the overall experience unique.