Channelling's direct ancestor is the trance mediumship of nineteenth-century spiritualism, in which a medium would enter a state resembling sleep or hypnosis and speak, often in an altered voice or manner, as a "control" personality understood to be relaying messages from the dead. What changed from the 1960s onward was framing and content: rather than claiming contact with a specific deceased relative for a grieving sitter, the new wave of channellers presented themselves as conduits for a single, named, ongoing entity with its own extensive teaching.
Jane Roberts began channelling an entity she called Seth in 1963, producing a lengthy series of books presenting Seth's philosophy of reality creation that became foundational texts for much of the later New Age movement. J. Z. Knight brought channelling to a much wider popular audience from 1977, presenting an entity she called Ramtha, said to be a 35,000-year-old warrior-spirit, through public seminars, videos, and eventually her own school, drawing celebrity followers and extensive media coverage through the 1980s.
Channelling spread widely through the New Age movement as both a spiritual practice, understood by practitioners as genuine contact with a higher or external intelligence, and a commercial one, with channelled teachings, books, and seminars becoming a significant part of the alternative spirituality marketplace.