Literary mood, also called atmosphere, is created by a combination of many elements including diction, setting, description and characterization. Mood is something that has a focus within the setting. It is sometimes confused with the narrator's "tone" but is different in that the narrator's tone (or tone of voice) has a focus outside the setting. For example, a calm narrator can tell a scary ghost story: the tone is calm the mood is scary.
As in all literature and drama, mood in created in Our Town by a combination of setting, diction, characterization, and description. Examples of how setting and diction contribute to mood are as follows.
Setting has a lot to do with mood in that the stage is starkly dressed, in fact, almost empty. Another element contributing to mood is that the scenes jump and time jumps with little feeling of a flow of continuity. In fact, the Stage Manager's speeches are needed to establish the continuity that is missing otherwise.
Diction is the choice of words and includes high, low, formal, informal, dialect, concrete, abstract. The vocabulary of the narrative established the mood as well and the tone of the narrator and the style of the author.
In this case, the diction is low and informal with some trace of dialect as in "our mount'in." the vocabulary is concrete talking about stars, mountains, main Street, churches; these are all concrete objects. The dialogue between characters is generally carried on in short sentences and often only one sentence per speaker: "Morning, Joe." "Somebody been sick, Doc?" "No. Just some twins born over in Polish Town."