This month we invite all fans of the ‘kitchen table’ series to build a classic auditory illusion that has had psychologists and neuroscientists puzzled for decades. Although we’re presenting a mini project built from a handful of cheap parts, it will not fail to produce stunning effects and results.This article is of the ‘zero-hardware / huge background’ variety and as such fits perfectly in our ‘kitchen table’ series of mini projects aimed not only at developing electronics skills but also at triggering experimentation. This month, a dead simple two-tone two-phase oscillator produces a mind-boggling effect (quite literally) — guaranteed to cause a good deal of wonder & excitement in the physics and electronics classroom.