Phantasmata = n. pl. phan-tas-ma-ta, from Greek phantasma. Images of the soul, mental images, something existing in perception only; Mental imagery (varieties of which are sometimes colloquially refered to as 'visualizing,' 'seeing in the mind's eye,' 'hearing in the head,' 'imagining the feel of,' etc.) is quasi-perceptual experience; it resembles perceptual experience, but occurs in the absence of the appropriate external stimuli. More on philosophical connotations of mental imagery here. The image is a process - and a predicate - of the brain, not a property of the world represented. "...nothing can ever be present to the mind but an image or perception..." (Hume, Enquiry XII.1)
Technique = Phantasmata is transformation of light into electricity and electricity into sound.
Instructions = Beware of your ears, close your eyes.
Collateral effects = Allucinations, synaesthetic visions, phantasmata.