What devices are used in Act 3, Scene 4, lines 61-87? What tone is created through these devices?

Macbeth uses hyperbole, or exaggeration, when he says that he looks on something "Which might appall the devil" (3.4.72).  He is referring to Banquo's ghost, the sight of which is probably awful to him because he is guilty of Banquo's murder, but the devil has likely seen worse.  This affects the tone of the scene because Macbeth describes Banquo's appearance as so frightening that even the most evil creature in the world would be scared...

Macbeth uses hyperbole, or exaggeration, when he says that he looks on something "Which might appall the devil" (3.4.72).  He is referring to Banquo's ghost, the sight of which is probably awful to him because he is guilty of Banquo's murder, but the devil has likely seen worse.  This affects the tone of the scene because Macbeth describes Banquo's appearance as so frightening that even the most evil creature in the world would be scared of it; this is dark stuff.  We can know, then, that Macbeth's fear of him must be incredibly intense, and it is caused by his own guilt, another intense emotion that is very uncomfortable.  Thus, we are made to feel uncomfortable and anxious as well.  

Lady Macbeth then compares Macbeth, via metaphor, to a woman telling a scary story to her grandmother.  She definitely implies that he is weak.  She calls him a coward and wants him to act like "a man" (3.4.70).  Just as Macbeth's exaggeration shows us how intensely fearful he is, Lady Macbeth's metaphor shows us how intensely she fears others finding out what they have done.  She fears that his guilt is getting to him and that it will cause him to accidentally reveal the truth.  Thus, we see how paranoid and anxious she is to conceal what they've done when she fears that her husband is losing it.  It is extremely tense for us, then, as well as her.

It is also a typical dramatic device of Shakespeare's era to employ a ghost.  Because the ghost has stage direction, we know that the audience is able to see him as well.  This would very much affect the feeling of the scene because Banquo's ghost would be an awful thing for us to see, in both senses of the word: he is terrible but also awe-inspiring, bloody and very angry.  It would heighten our tension as well.