Final answer:
Macbeth is the speaker in the scene at Macbeth's castle where the solemn banquet for the deceased Duncan is taking place and Banquo is murdered.
Step-by-step explanation:
In the scene at Macbeth's castle where the solemn banquet for the deceased Duncan is taking place and Banquo is murdered, the speaker is Macbeth.
Macbeth speaks in multiple lines throughout the scene, expressing his guilt, fear, and paranoia. He interacts with Macbeth and other characters, discussing the events that have transpired and the consequences of their actions.
For example, Macbeth speaks to the ghost of Banquo, who only he can see, revealing his disturbed state of mind. Lady Macbeth also speaks in this scene, though her lines are limited in comparison to Macbeth's.