Shepard Tone Generator

Shepard Tone Generator is a free online tool that plays the Shepard tone, an auditory illusion of a sound that keeps rising (or falling) in pitch forever, without ever actually getting higher or lower. Play it directly in your browser, choose between the smooth version (the Risset glissando) and the classic version made of notes (the Shepard scale), make it ascend or descend, change its speed and its pitch, and download it as a WAV file.

How to use this online tool?

Choose the type and the direction of the tone, adjust the speed, the center frequency, the number of octaves and the volume, and click on the button "Play". You can change every option while the tone is playing, and switching the direction makes it turn around right where it is. Then, click on "Stop" to stop the audio.

To generate and download a Shepard tone audio file (WAV file), choose the options and the duration (in seconds), and click on "Download". The file loops seamlessly, so it can also be repeated in other software.

How does the Shepard tone work?

A Shepard tone is not one sound but several sine waves played together, each exactly one octave above the previous one. All of them rise in pitch at the same time. Their volume follows a bell shaped curve: the sine waves in the middle of the range are loud, and the ones near the bottom and the top are quiet.

As a sine wave rises towards the top of the range, it slowly fades out, and at the same moment a new one fades in at the bottom. Your ear follows the loud sine waves in the middle, which are always going up, and never notices the ones that silently leave and arrive at the edges. After rising one full octave, every sine wave has taken the exact place of the next one, and the sound is back where it started, even though it seemed to go up the whole time.

The illusion works because an octave sounds like "the same note" to the human ear. It is the auditory version of the barber's pole, whose stripes seem to rise forever, and of the Penrose stairs, a staircase that goes around in a loop while always climbing.

Shepard scale and Risset glissando

The original version, created by the cognitive scientist Roger Shepard in 1964, is a scale of separate notes: each note is one semitone above the previous one, and after twelve notes the scale starts over without seeming to. That is the Steps option of this tool.

The composer Jean-Claude Risset later created a continuous version, in which the pitch glides smoothly instead of moving in steps. It is known as the Risset glissando, or the continuous Shepard tone, and it is the Continuous option of this tool.

Where is the Shepard tone used?

The Shepard tone is a favourite of film and game composers who want to build a feeling of tension that never resolves. It is the sound of the endless staircase in Super Mario 64, and it shapes the score of Christopher Nolan's film Dunkirk, composed by Hans Zimmer, where the music seems to rise for the whole movie. It is also used in psychology and in the teaching of acoustics, as a striking example of how the brain perceives pitch.