An Imp is part of the seduction.
Someone asked in an email what the difference is between an Imp and just "presentation." Am I just making up terminology? No, I'm not. Well... I am just making up terminology, but there is a reason behind it.
If you take an Imp and flesh it out and explain it to the audience, then it can become a presentation.
But not all presentations are Imps. "Do you know the difference between a magician and a gambler?" isn't an imp. It's a presentation (one that suggest you think your spectator might be a moron).
And not all Imps are presentations. Remember, snapping was the first Imp I discussed here. No one would say snapping, or waving a wand, or casting a shadow is really a presentation. The Five Movements is an Imp that might imply a presentation, but if you don't spell it out for people it remains an Imp.
That brings me to an important point. There are three ways you can introduce an Imp into your effect: explicitly, implicitly, and arbitrarily.
Let's take them in reverse order.
Arbitrarily
Let's go back to the concept of using white noise. Here's what you shouldn't do. "I'm going to play white noise and it's going to influence you to match up the cards." This is a meaningless statement. It's as meaningless as saying, "I'm going to eat a cheese sandwich and it's going to influence you to match up the cards."
Coming out and baldly stating some arbitrary connection between the two things is just going to get rejected as obvious horseshit. People have a natural resistance to arbitrariness. So you don't want the connection between the impetus and the effect to come off that way.
Instead of handling an Imp arbitrarily, you need to handle it implicitly or explicitly.
Implicitly
You play the white noise. You look in their eyes. You switch to another color noise and examine their eyes. Then you switch again. Satisfied, you have them deal out the cards and stop twice burying face-up cards in the deck each time. At the end, the cards they stopped at match the cards they put in the deck.
"What was that noise thing about?" they ask.
"Oh nothing. That's just... it's nothing. Are you hungry? We should get a pizza."
When you say, "This white noise is going to control your decisions." You're just giving them something to reject as totally baseless. But if you just imply the white noise is important (by paying attention to it for a moment), and then perhaps even deny that it is later on, you can get them to strengthen the link in their head between the impetus and the effect.
Remember what I said above: people have a natural resistance to arbitrariness. In this case we are going to harness that for are own purposes. When you don't justify the purpose of (in this case) the white noise, their aversion to the arbitrary will push them the direction you want them to go. "Well, he didn't just play that noise for no reason. So there must be some connection between that and the effect. But what could that be?" You're getting them to force the issue. Now, ultimately they may come to the conclusion that it's all part of the charade. That's fine. But at least you get them to consider it in a way they wouldn't if you were the one pushing the connection.
Explicitly
The final way to handle an Imp is explicitly. That is, you spell out the connection between what you're doing and what happens. An explicit imp is an understandable story of cause and effect.
"I'm going to play white noise and you'll deal to the cards I choose," is not an understandable story. How does one thing cause the other? You need to add some elements and give your spectator some path to follow.
It doesn't necessarily need to be believable. It just needs to be understandable. In fact, I'll break this down even further. You can have Believable Explicit Imps and Fantastical Explicit Imps.
Fantastical Explicit Imp - "This box contains stuff that belonged to my grandfather. This record was his favorite. Sometimes when I play it weird things happen." You play the record and one of the items you dumped from the box—let's say, a bottle cap—flies across the table.
The Imp is playing the record. It's an Explicit Imp because you're saying playing the record will cause some phenomenon to happen. It's a Fantastical Explicit Imp because you're dealing with a cause and effect that is profoundly unbelievable. But even though it's still a mysterious/weird cause and effect, it's one that's easy to understand. It's not arbitrary. You play your grandfather's favorite record and his spirit or energy causes something else of his to move. That "story" makes sense.
Believable Explicit Imp - These are things like hypnosis, influence, and reading body language cues. An effect that uses a BEI can still have a climax that feels magical and unreal, it's just that the connection between the impetus and the effect isn't inherently unbelievable.
I like both these styles. FEIs are like little immersive Twilight Zone moments. BEIs are like a vignette from Mr. Wizard but with an amped up ending.
I'll leave you with this.
The effect is Gemini Twins.
White noise is the Imp.
"Believable Explicit" is the style of Imp.
The effect is...
Tiki and Ronde
You spread a deck of cards face up on the table.
"Have you heard of black noise?" you ask.
"Let me find some on youtube." You open your laptop and start playing something. Your screen is turned away from your spectator. It sounds like static-y fuzz.
"You've heard of white noise, right? And you may have heard of other variations of it, like brown noise or pink noise. They're supposed to have different effects on you in regards to things like relaxation and concentration."
"Well, black noise is this relatively new thing they've discovered. I don't know what it is. Like a new wavelength or something? And it's supposed to affect areas of the brain in regards to perception and suggestibility. Can we try something weird?"
You scoop up the deck and remove the jokers from the bottom. Your spectator deals through the deck, stopping twice whenever she wants to place the jokers face-up into the deck. When she's done you ask her to hold onto the deck.
"That was a free choice? Where you put the jokers, I mean. You just went off instinct?"
"And when I had the deck spread face-up on the table when we started, you didn't, like, consciously memorize the order or anything like that, right?"
She agrees.
"Okay... let's see what happened," you say.
You tell her to turn the laptop towards herself.
She does and she finds that it's not precisely what she thought. It's not a single youtube video. It's actually a site that is playing two videos simultaneously. The one labelled "Black Noise" is playing loudly. The volume on the other one is turned down very low. The title on that video is, "Card Station, Pinedale, Wyoming 5/8/73."