With regard to its belonging within the category of either Mental Mediumship or Physical Mediumship, Trance Medumship as such is a bit of a 'Grey Area'. There are indeed so many different 'Levels' and depths of trance, between the state of being 'Overshadowed' and being in 'Deep Trance', where a medium is totally unconscious and unaware of anything that is happening within themselves and around them. I believe that it is better to simply refer to any level of trance as an 'altered state', as this is a more accurate description of every level.
It can be argued logically in most cases that, even if an entranced medium is aware of every word that is spoken through him or her, the medium has no physical control over the content of what is said. Other than when a medium is in a very light trance (overshadowed), this is essentially an accurate statement.
If this is indeed the case, then it can further be argued that - since the medium has no physical control over the content of what is spoken through their own larynx whilst they are in this altered state - the process of a spirit person speaking through them in this way is an aspect of physical mediumship.
Whilst I can personally see the logic of this argument, I do not regard trance mediumship as such as an aspect of physical mediumship but - simply - in some cases (not all) a tool to enable the production of physical phenomena when properly managed by a 'team' of spirit personalities who work with a particular medium.
Sometimes we have to be careful not to mix up the terms which are used for a type of physical phenomena with a trance communicaton through the human larynx of a medium. I know of several experienced psychic researchers, for instance, who have gone for a private sitting with a trance medium who advertises 'direct voice', only to discover that instead of physical phenomena, they have simply been treated to trance communication through a medium. It might be an honest mistake to make on the part of the medium, but it can be very misleading and, hopefully, we can help to set the record straight.
However, when sitting specifically for physical phenomena in the more traditional way - ectoplasmic-based - the single physical medium involved is usually in a 'deep trance' state. There are exceptions to this; the famous Independent Direct Voice medium Leslie Flint comes to mind here, as Leslie was fully awake during his sittings and was able to join in the conversations with the spirit voices that occurred through his mediumship.
When a medium is capable of producing full ectoplasm-based materialisations, however, it does seem essential for them to be in a deep trance throughout this process.
This is not necessarily the case where an experimental group is sitting for physical phenomena in the more modern energy-based way, where no ectoplasm is involved in the process. It is true that one or more of the group sitting in this way may be used in trance. That is particularly helpful when an experimental group first starts sitting to develop physical phenomena, as communications and instructions to help the group with their development can then be received in that way. Throughout the history of the Scole Experiment in the 1990's (where the energy-based method was pioneeed) we had two of the group members in deep trance throughout the sittings, but the Scole Group was unique at that time.
These days, we have been told by our spirit helpers that trance is not always necessary at all for phenomena to be produced in the energy-based way. In fact, Sandra and I sat for some time in an experimental group in South London, who had amazing physical phenomena where nobody at all went into an altered state. The group did not even know who the medium of the circle was at the time, although we did eventually discover his identity. The gentleman had no idea himself!
The more likely scenario today is that one or more of the sitters might be used in an altered state to bring through communications from the spirit team who work with the group in an energy-based format, but when this happens the trance state will not be as deep as when the circle are developing in the more traditional ectoplasm-based format.
I must stress here, however, that neither way of working is better than the other. They are just different ways of working, and an equal amount of dedication, love, patience, harmony and determination is necessary to develop positive results. It is true that the energy-based format has certain advantages, which I will go on to explain soon on this site.