Be not afeard. The isle is full of noises,
Sounds and sweet airs that give delight and hurt not.
Sometimes a thousand twangling instruments
Will hum about mine ears, and sometime voices
That, if I then had waked after long sleep,
Will make me sleep again; and then, in dreaming,
The clouds methought would open, and show riches
Ready to drop upon me, that when I waked,
I cried to dream again (3.2.148-156).
Is Caliban actually experiencing Prospero's attempt to influence his humoral balance here? (Music was thought to alter a person's humors, and--from that perspective--the "noises" Caliban hears might actually be trying to manipulate his state of consciousness, forcing him indeed to "sleep again," if Prospero wishes it.) If so, this sleep is extremely dangerous, because it's externally induced, and essentially tortures a slave--taunting him with riches, so that he "cries" when he is forced to wake. Or, alternatively, is this sleep actually a state of escape, which Caliban can use to temporarily leave his enslaved status behind? Even if that's the case, it's also worth noticing that states of consciousness are being manipulated by external instruments and voices here, and the power dynamics of both colonialism and early modern humoral medicine are very much in play.
Knowing this background, to put these words in the mouth of a famous Shakespearean actor is one thing. To put them in the mouth of a famous Shakespearean actor dressed up as a Victorian business mogul (one galvanizing the Industrial Revolution, no less!) opens up a wide range of possible overtones, some of which clash a little with each other. A powerful man in top hat and tails, rejoicing as workers create smokestacks, sounds more like Prospero than Caliban--and the riches that he gained from his work were no doubt more material than illusory. In the context of last night's performance, then, Caliban's speech served a number of rhetorical functions: it represented the luxurious language of a national-treasure playwright, but it also carried traces of colonial interactions and medical discourse, which clashed and merged with the Victorian/Olympic/Branagh context in a jarring but interesting way.