Trance is a form of advanced mediumship where a spirit person uses the medium’s body and voice to communicate with others, usually in a séance. It is not to be underestimated in seriousness, as it is a form of possession. It is very dangerous to attempt if one hasn’t a high level of mediumship experience.
Mediums in trance often appear physically different while in trance, taking on the persona and mannerisms of the spirit person, and can even speak in different voices and languages that they have no prior knowledge of.
There is also a light trance state, sometimes referred to as overshadowing or overtaking, which happens when guides and/or spirits who are already communicating with the medium during a séance or paranormal investigation almost channel their own voice through the medium’s voice box.
This overshadowing can make the medium feel as if their features or bodily form are changing from the norm, or that they have taken a step back and someone else is trying to steer their thoughts and speech. It is similar to transfiguration but more physical and much stronger in feeling.
The medium may feel heavy headed and unable to speak for a few moments, with particular pressure around the larynx or throat chakra.
This should never be attempted without supervision, as there is training required for a “buddy” to bring you back forward if you are overshadowed for more than a few moments. It is not to be underestimated in seriousness, as it is a light form of possession, only to be undertaken by experienced mediums.
One of the most well known accounts of trance mediumship is that of the spirit guide Silver Birch and his medium. Do a Google on the name and see what you find!