The Shepard Tone Machine

The Shepard Tone is an auditory illusion created by layering sine waves one octave apart. Each wave sweeps upward (or downward) continuously while a bell-shaped volume envelope fades them in and out.

Your brain blends the layers into a single percept that appears to rise forever — like an audio barber pole or an M.C. Escher staircase. It never actually arrives anywhere.

Roger Shepard invented it in 1964 as the sonic equivalent of the Penrose impossible staircase. Hans Zimmer used it in Dunkirk to build relentless tension. Super Mario 64's endless staircase uses it too.

Try it: set layers to 2, then increase to 8 — hear how the illusion strengthens. Toggle "Break illusion" to hear where the tones wrap.