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For those of a certain age, or maybe a love of retro gaming, you might remember SUPER MARIO 64 and the infinite staircase. You’re running forever to get to Bowser at the top. You weren’t being chased; you just had to keep going. The music did the same thing.

Mario looks like he isn’t even moving.

The GIF below is the visual version of the Shepard tone.

However, unlike the real Shepard tone, you can get out of the staircase with 70 or 80 Power Stars (depending on your version).

Last time Bell Labs came up, it was Involuntary Hallucination. This time it's Roger Shepard (of Bell Labs), a cognitive scientist who published a paper in 1964 with a title only an academic could love (and you and us): Circularity in Judgments of Relative Pitch.

A true evil genius, he built a tone that continues to rise forever. Somehow, every ‘step’ or sound seems to get higher than the last one. The worst part about it, to our ears and expectations, is that it doesn’t actually get higher.

We’re used to being tricked by countless other things already. Bass that’s not real, gaps in music our brains fill, the difference in how two people hear the same music.

So this particular trick works because there isn’t one note. Well, technically, it is the same note stacked across several octaves, all playing at once. C, the C above, and the C above that.

But to make it work, the volume of each note is different. The note in the middle of the stack is the loudest, and the top and bottom are left quieter. As the highest note fades out, a new one fades in at the bottom, so it sounds like it is rising, but it never actually gets any higher. Some people will feel panicked from listening.

Everything points to ‘up,’ so your brain follows it and registers it as climbing. What it can't track is which octave you're in. That's octave equivalence: a C is a C, high or low. Once it all gets blurred, there is no end; it can go forever.

It was taken further, like most things in music are, by Jean-Claude Risset (also at Bell Labs). He made it even smoother, so that you couldn’t make out any of the ‘steps’ as it rose. It just felt like one long note, climbing up. That's the Shepard-Risset glissando, and it's the version you've heard in cinemas, the one that starts your heart pumping.

Music ebbs and flows. It is always doing something, like a catch-and-release program for your brain. We spoke about that, and rewards for anticipation and payoff in music in Run It Back. The Shepard tone is horrible, just anticipation. With no payoff ever. So, your brain that loves the payoff never gets it; it just keeps building. That, and it has been used on us for decades in movies to build up to something that will get your heart racing. We’ve been Pavloved by a C note.

We can point you in the direction of people who have used it a lot. Christopher Nolan said he wrote the DUNKIRK script according to the Shepard tone principle, and Hans Zimmer layers the effect heavily. THE DARK KNIGHT's sound designer used it for the Batpod. Queen open and close A DAY AT THE RACES with one.

Put a Shepard tone on and hum along. Follow it up. Keep going. Your voice will hit your ceiling before the tone does, because the tone doesn't have one.

Then see how long you last. Because this one isn't just a party trick.

Rebecca Mursic, a psychology researcher at the University of Wollongong in Australia, studied it. Some of her participants got actual motion sickness: nausea, wobbly balance, the works. Most got nervous and agitated. A few found it relaxing. One person compared it to morphine. Another got properly angry. And after a long day of testing it on other people, it got her too, which we understand after having it on while we were researching it.

So, five minutes is a limit. Ten if you're very brave. But if the room starts to tip, turn it off.

Want to hear it? Of course.

There's also the tritone paradox, where two people hear the same notes going in opposite directions. We'll get into that another week...