Double, double, toil and trouble; / Fire, burn; and cauldron, bubble.
Act IV, Scene 1 · The Three Witches
Context
The three witches chant this refrain repeatedly as they throw ingredients into their cauldron, preparing a spell before Macbeth arrives at their cave.
Analysis
The driving rhythm of paired monosyllables—'double, double,' 'toil and trouble,' 'burn' and 'bubble'—mimics the relentless, hypnotic repetition of stirring a cauldron, pulling the audience into the witches' ritual as if under a spell themselves. The hard alliterative sounds (d, t, b) give the chant a percussive, incantatory force that makes the supernatural feel physically present and threatening, not distant or abstract.
Essay Tip
Use this to argue that Shakespeare makes the supernatural convincing through sound, not just content—the rhythm itself performs the magic, training the audience (and Macbeth) to fall under the witches' influence before any prophecy is even spoken.