Shepard Tones at last

[KA4HJH]

>>I now have a sample of the Shepard Tones (only ten months after we
>last
>discussed it). Does anybody have a place I can put it? It's rather
>large...

>
>Hi Terry- How did you do these and how big are they? Has anyone else
>come forward with a place for them?

John:

I have a 1.3 MB .wav file which is about a one minute sample taken from a
cassete tape which was released by CCMRA as a companion to the book *The
Science of Musical Sound* (out of print). It sounds pretty good (16 bit,
11K) and illustrates the illusion perfectly. All it needs is a home. I've
had it for a long time and just never got around to telling anybody (it's
been a rough year, folks).

----------
For those whose don't want to bother looking it up, here's my original
posting from April 7, 1997:

René:
You're referring to the famous "sonic barberpole" illusion invented by
psychologist Roger Shepard at Bell Labs. The illusion consists of a
seemingly endlessly rising or falling set of tones. The trick is done by
simultaneously sweeping eight (or so) sinewaves tuned exactly one octave
apart. The human ear has a really hard time figuring out which pure tone is
the fundamental, so it "slips" periodically, just like an eye watching a
barberpole (or looking at an Escher staircase). To conceal the tones'
appearing and disappearing they fade in at one end of the cycle and fade
out at the other.

To create the Shepard Tones in the analog domain you need eight VCO's,
eight VCA's and an LFO with ramp and triangle outputs in octature (eight
outputs 40 degrees apart). Harold Bode used phasers instead of VCO's to
create his famous "Barberpole Phaser." PAiA used to have a Shepard Function
LFO kit, although I think it's long gone now.

[there may still be a schematic at...]
http://www.hyperreal.com/machines/categories/midi-cv-sync/Paia/image

I could post a sample if anyone's interested; it's too late for me to do
tonight. [HA]


The Science of Musical Sound--John R. Pierce, Scientific American Library
"Lab Notes: Shepard Functions"--John S. Simonton, Jr., Polyphony, 2/83

[And that's the way it was...]


Terry Bowman, KA4HJH