In A Streetcar Named Desire, what expressionist devices are coupled with the doctor's arrival, and what is the resulting effect?

When the doctor arrives in the final scene to take Blanche away, Williams's stage directions call for the "varsouviana" to play in the distance. This "rapid, feverish polka tune" both reflects Blanche's inner turmoil and evokes her shady past, since the boy she was in love with killed himself after they danced the varsouviana together. During the dance, Blanche had told the boy that she knew about his homosexual relationship with an older man and that she was disgusted by it. Along with the music, visual images also appear in the form of "lurid reflections" on the walls in "odd, sinuous shapes." The shadows suggest confusion and violence and recall Stanley's rape of Blanche in the previous scene.