Shepard

this tone rises forever. it never gets higher.

an endlessly ascending tone — hold it, time it, disbelieve it

A tone that seems to keep climbing is actually cycling: layers fade in at the bottom as others fade out at the top, so the ear hears endless ascent while the actual pitches loop forever. There is no trick to catch — just the strange fact that hearing cannot tell rising apart from looping.

Concepts: sound, illusion.

An interactive you play with one thumb, on Wundr.