What two factors often lead to a composer writing film music?

Read the following scene from trifles. mrs. hale (resentfully). i don’t know as there’s anything so strange, our takin’ up our time with little things while we’re waiting for them to get the evidence. (she sits down at the big table, smoothing out a block with decision.) i don’t see as it’s anything to laugh about. mrs. peters. (apologetically). of course they’ve got awful important things on their minds. (pulls up a chair and joins mrs. hale at the table.) how would an audio recording most likely convey the characters’ emotions during this scene?