| Quote #4
and, while the chimes of the clock yet rang, it was observed that the giddiest grew pale, and the more aged and sedate passed their hands over their brows as if in confused reverie or meditation. (5)
The eerie chimes of the big black clock seem to be another reminder of death – they indicate that time is passing. This also makes the revelers nervous…particularly the ones who are closest to death (the "aged and sedate").
| Quote #5
But to the chamber which lies most westwardly of the seven, there are now none of the maskers who venture; for the night is waning away; (7)
As the night draws on and the midnight hour approaches, the nervousness of the revelers increases. Whereas before there were few willing to go into the black room, now there are none. This helps to create a sense of mounting fear.
| Quote #6
And the rumor of this new presence having spread itself whisperingly around, there arose at length from the whole company a buzz, or murmur, expressive of disapprobation and surprise --then, finally, of terror, of horror, and of disgust. (8)
The new masquerader – the guest in the Red Death costume – makes everybody uneasy, especially since he appears at the stroke of midnight (when they're already nervously stopped at the sound of the clock). Notice how their reaction changes from one of mere surprise or disapproval to actual terror. The sense of fear continues to grow.