Hilary Mantel, when describing how she writes, refers to a passage near the beginning of her earlier novel Beyond Black, about a performing medium, Alison:

She takes a breath, she smiles, and she starts a peculiar form of listening. It is a silent sensory ascent; it is like listening from a stepladder, poised on the top rung; she listens at the ends of her nerves, at the limit of her capacities. When you’re doing platform work, it’s rare that the dead need coaxing. The skill is in isolating the voices, picking out one and letting the others recede.