A precursor to modern sound and light devices such as the Brain Machine, Brion Gysin and Ian Sommerville’s Dreamachine –

In its original form, a dreamachine is made from a cylinder with slits cut in the sides. The cylinder is placed on a record turntable and rotated at 78 or 45 revolutions per minute. A light bulb is suspended in the center of the cylinder and the rotation speed allows the light to come out from the holes at a constant frequency, situated between 8 and 13 pulses per second. This frequency range corresponds to alpha waves, electrical oscillations normally present in the human brain while relaxing.

A dreamachine is “viewed” with the eyes closed: the pulsating light stimulates the optical nerve and alters the brain’s electrical oscillations. The “viewer” experiences increasingly bright, complex patterns of color behind their closed eyelids.

Dreamachine on Wikipedia

More info and build documentation regarding the Dreamachine is available from Kaden Harris’ Eccentric Cubicle – The Gysin Device
In the Maker Shed:

Eccentric Cubicle