what do you mean?
@Ringo
It gets a little complicated but here goes. There are 3 types of Seance Shows or Theatrical Seance.
1. There are "spooky" magic shows called seances but they are just a string of magic tricks with a spooky or horror theme, performed by a magician who is in the little known magic category of "Bizarre". (I'm not being sarcastic, the genre is actualy called that). They buy ready-made, out of the box tricks with themes like JTR Seance or The Titanic seance which include loads of scary, old looking props and photographs and expensive, aged paraphernalia. These guys are usually hobbyists who perform mostly for other bizarre magicians as there isn't really a big market for this stuff. They learn the script and then perform it. It takes very little preparation or skill and can come off as either fun or sick.
EDIT: The can sometimes get stuck in the details of a trick and spend years expanding it, reading variations, elaborations and twists but in the end, it's more for the arts sake than anything else. The audience will have stopped listening long before that. It's more for other bizarrists to nod sagely.
2. Then there are "seance" experiences which is a bit like an amusement ride. They are operated by companies using technology and basically any summer-job kid can press that start button and hand out cloakroom tickets. A bit like an Escape room experience, you turn up as agroup and are ushered into your "experience" room. They press go and off it goes. Fun but you are passive to the experience.
3. Then there are proper "seance" shows or "theatrical seances" where it seems so real. The mentalist or performer is so believable, the room so innocuous, the psychology so powerful that things "happen by themselves". (They don't really but that's how you remember it). This takes years and years of experience, refinement, research and development, trial and error, script writing, costume design, prop building, people skills, acting, music etc etc. It is all scripted and timed to the second but you will never know as it seems 100% real and relaxed. The idea is to co-erce a "genuine" response from the audience and to make people believe they have witnessed real life paranormal phenomena (even when they know they have bought a ticket to a show). You destroy the line between reality and fiction.
All of these are "theatrical" performances - as in, they would be marketed as shows rather than trying to be passed off as a genuine psychic night or a spiritualist evening. People attending know that it is fiction and choose to buy into it. The 3rd kind is what I would call a "proper" seance show (and what I try to do).
EDIT: One final thing - this from the Wiki page about Theatrical Seance explains nicely the difference between a theatrical seance (what Mentalists do) and Spiritualist Seances (what mediums do):
Theatrical séances are not intended to be "real" séances and should only be seen as entertainment; hence the adjective, theatrical. According to Houdini, if the séance leader is honest and admits his trickery, he is a theatrical performer; if not, he is a charlatan and a fraud. Ethically, a paying audience should be notified beforehand that they will be experiencing a work of interactive theater rather than an actual Spiritualist seance. Once the audience is inside the performance space, however, the performer's primary responsibility is to create a convincingly realistic theatrical experience, just as in other forms of theater. Additionally, the ambiguity of whether every manifestation is the result of deception or not may be part of the enjoyment that a theatrical seance provides.