Friday Tips: Create the Barberpole Audio Illusion

The Shepard Tone (aka Barberpole) is an audio illusion where a tone always seems to keep rising (or falling). You may have heard it before-to build tension in music by Swedish House Mafia, Beatsystem, Data Life, and Franz Ferdinand, as the sound effect for the endless staircase in Super Mario 64, for the sound of constant acceleration for the Batpod in The Dark Knight and The Dark Knight Rises, at the end of Pink Floyd's Echoes from the Meddle album, or in the soundtrack for the film Dunkirk in sections where the goal was to produce a vibe of increasing intensity. Check out the audio example, and you'll hear how the tone just goes on forever.

Thanks to Studio One's Tone Generator, it's easy to produce a Shepard Tone loop-just follow the step-by-step instructions, in a song with the tempo set to 120 BPM.

Insert the Tone Generator in the Input L+R insert section so that you can record its tone, and edit the Tone Generator generator's settings as shown in the screen shot. The goal is the longest possible sine wave sweep from 20 Hz to 22 kHz.

Start recording, then click the Tone Generator's On button. After recording the file, trim the beginning and end respectively to just before and just after you can hear a tone, and add a short fade in and fade out.

As shown above, copy the track, and offset each track's beginning by two measures compared to the track above it. Keep copying and offsetting until the start of the last track is at the same measure as the end of the first track.

Now select all, and drag the entire group to the right so that there's a bit of an overlap between the two groups. Select everything, then type X to turn the overlap into a crossfade with a linear curve. Next, create a loop that extends from the start of the lowest track to the end of the highest track.

Choose Song > Export Mixdown, set the Export Range to Between Loop, and under Options, check Import to Track and Close After Export. Solo the mixed track, and play it-you'll hear a continuously rising tone. Now we need to turn it into a loop.

Follow the instructions in the July 27 Friday Tip of the Week on how to create pads that loop perfectly. The above screen shot shows the basic concept; Track 1 shows the first steps. Copy the clip, move the copy to the right so it overlaps the last four measures of the original clip, and then crossfade the overlap with a linear crossfade.

Track 2 in the screen shot shows the next step. Bounce the two clips together, then split at the end of measure 4 to remove the first four measures, and at the end of the crossfade to remove everything after the crossfade. Loop the section that remains, and you have your never-ending upward Shepard Tone, as a glitchless loop. Note that when you bring it into a project, don't stretch it to conform to tempo-there is no tempo. And if you want it to go on forever just keep typing D!

Download the loop here!

Bonus Tips:

I recommend adding a Pro EQ-reduce the high frequencies somewhat with the HC (High Cut) filter, and boost the low frequencies with a bit of a shelf, to increase the illusion's effectiveness.

The classic Shepard Tone requires that the tones be one octave apart. However, offsetting them by 2 measures at 120 BPM seems close enough.

LINK:	http://blog.presonus.com/index.php/2018/09/21/friday-tips-create-barbe...
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