Looped pitch stimuli can generate an endlessly ascending scale that never actually climbs

Evidence

A pitch illusion, which has been compared with the continuous staircase pictures of Maurits Escher, has been demonstrated by Shepherd (1964) and is often referred to as a “Shepherd tone.” This illusion produces the sensa­ tion of an endless scale which ascends in semitone steps. After 12 semi­ tone steps when the pitch has risen by one octave, the spectrum is identical to the starting spectrum so the scale ascends but never climbs acoustically more than one octave. — David Howard, Jamie Angus, coustics and Psychoacoustics, 1683

Categorization

• XREF: The Shepherd tone is an endlessly recurring audio illusion that connects directly to the illusions literature I’ve curated on silence and perception.
• CANDY: The never-ending ascending scale that never rises is a fun conversational fact alongside Escher staircases.