Chapter 9 considers Victorian practices of mesmerism in the context of ongoing debates in the period as to whether a conscious, rational individual might be made to behave in certain ways through unconscious influences. The fundamental premise of mesmeric practice – the transmission and reception of nervous energy by way of the imponderable vibrations of the magnetic fluid – was, I argue, grounded in acoustics. Sound and music played a critical role in inducing trances and triggering responses, while also providing a potent series of auditory metaphors by which these unusual states of being might be framed and understood. The mesmeric bond between individuals was believed to operate as a form of communication network, which transcended the limitations of the individual body and its sensory capacities, while also pointing to the potential forces and energies that might operate beneath the threshold of human consciousness.