how are audio and lighting effects important in a Streetcar named Desire?

A Streetcar Named Desire uses lighting and stage effects to exacerbate the drama onstage and to include the audience in the scene. the lighting changes according to both Blanche and Stnaley's moods showing them as major characters and the continuous use of certain types of music during Blanche's manic episodes alert the audience to the significance of these and the importance of these ot her character. Music also creates tension and drama and puts the audience on edge awaiting further drama.