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Shepard Tone Generator in DIY?
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Shepard Tone Generator in DIY?
Reality Checkpoint
I have long been fascinated by Shepard tones and was wondering whether there is diy generator project.

I presume that it would have to be digital rather than use a whole case full of sine wave generators and VCFs etc. I would love to be able to produce Shepard-Risset glissandos from a single module, preferably banana/4U, for my burgeoning CGS/LW Serge system.
lacsap
Nice idea. so far I've mostly used Sheppard tones in SuperCollider. implementing those on e.g. a Teensy shouldn't be too complicated. Would be nice to also directly implement an envelope so you could play shepard chords. If I find time in the next days I'll give it a try.
There are some diy projects that already use a Teensy 3.2 microkontroller. the music thing radio music seems like a good starting point to "hack"

For an analog implementation eek! one could use Thomas Henrys Mankato filter in self oscillating mode. It produces 8 phase shifted sines. So now you'd be just needing 8 VCOs and 8 VCAs help ...
diophantine
PAiA published info on a Shepard tone generator in Polyphony in 1983. Obviously there's probably no PCBs currently available, but you can download the details on the EK-9 here:
https://www.paia.com/talk/viewtopic.php?f=6&t=184
Schlumpfhut
lacsap wrote:
So now you'd be just needing 8 VCOs and 8 VCAs help ...


One could Use Oakley SVCO and quad-VCA modules. 12 U in total so it should be doable in a reasonably sized modular....
the bad producer
lacsap wrote:
Nice idea. so far I've mostly used Sheppard tones in SuperCollider. implementing those on e.g. a Teensy shouldn't be too complicated. Would be nice to also directly implement an envelope so you could play shepard chords. If I find time in the next days I'll give it a try.
There are some diy projects that already use a Teensy 3.2 microkontroller. the music thing radio music seems like a good starting point to "hack"

For an analog implementation eek! one could use Thomas Henrys Mankato filter in self oscillating mode. It produces 8 phase shifted sines. So now you'd be just needing 8 VCOs and 8 VCAs help ...


Ah, the Mankato! I'd forgotten about that, but how to derive the phased sawtooth from the sine? A Teensy based module is a great idea indeed!
commodorejohn
Now I've got the urge to try something kooky like a single VCO FMed by a sawtooth LFO and LPF and HPF clamping down on the ends of the modulation range, run into an extremely short delay with the feedback up, or something...
lacsap
the bad producer wrote:

Ah, the Mankato! I'd forgotten about that, but how to derive the phased sawtooth from the sine? A Teensy based module is a great idea indeed!


sure for the pitch it's not a linear slope. Albeit a sine is perfect for the amplitude modulation of each oscillator, as each osc smoothly fades in and out...
Reality Checkpoint
A quick bump for this.

I certainly do not have the necessary skills to produce something like this, but would be very interested if someone could make one!
onurkalaycioglu
i might be interested in resurrecting this design, but i have a lot on my plate as far as new releases go. so probably wouldnt be able to get to this project until next year. cant make any promises that it will happen, but im a huge fan of shepard tones and i try to recreate their texture pretty often in my modular music.

i googled around a little bit but couldnt find anything. does anyone have a picture of what the ek-9 actually looked like? i mean the front panel.
Reality Checkpoint
onurkalaycioglu wrote:
I might be interested in resurrecting this design, but i have a lot on my plate as far as new releases go. so probably wouldn't be able to get to this project until next year.


That's all I need - a bit of hope! Thank you.

I haven't been able to find a picture od the EK-9 panel either. Doepfer used to manufacture the A191: http://www.doepfer.de/a100_man/A191_man.pdf which was a combination of a MIDI to CV interface and Shepard Generator.
KSS
EK-9 never had any official panel. Experimenter's Kits from PAIA were just that, with only PCB and some components, based usually on one of John Simonton's explorations published in a nationwide electronics magazine or later in PAIAs own Polyphony. Any EK-9 panel you might find will be someone's personal panel.

As for shepard tones in general, wasn't much impressed with them using the EK-9 kit, or the PAIA patches then suggested. Never really felt the endless rise or fall the effect is supposed to have. Could rather hear quite clearly the repetition and it got boring quickly.

Based on that, would suggest patching something up either hardware or software to be sure the result is good enough to be worth any additional effort.

Agree that Mankato's would be an excellent starting point.
EATyourGUITAR
Blacet had a PCB long long time ago I think.
andrewF
You can do Shepard tones, or something like them, with a frequency shifter. J.Haible described how to do it with his design, can't remember if it was here or on electro-music.

An easier option, I'm releasing a 12 hour sloth in a couple of weeks which will put out voltages that slowly rise or fall over a 4-6 hour period and cover 1-3 volts. It won't be an illusion, that pitch is really rising or falling and it definitely makes you tense hihi
Grumble
I did Shepard Tones on a module I’ve built using three YM2194 psg’s, so a total of 9 generators, unfortunately all square waves.
Midi controlled using Fruity Loops.
EATyourGUITAR
don't forget there is a shephard tone patch you can do %100 doepfer
loki
To hear a musical use of Shepard's tones go to YouTube and listen to Jean Claude Risset's Suite for Little Boy. It dates all the way back to the sixties and was generated on computer at Bell Labs.
lacsap
this evening I found some time to fiddle together some code to have a basic shepard tone on a teensy 3.2. nothing is optimized but merely quick and dirty ported from adc's Supercollider implementation.

the code outputs a shepard tone with 8 sines via USB, split between left and right. Before uploading you have to set the USB Type to Audio in Arduino in order for it to work. I also set the CPU Speed to 96MHz. In order to upload the sketch I renamed it from ".ino" to ".txt", just rename it again to open it in Arduino.
Quote:

Tools > USB type > Audio
Tools > CPU Speed > 96MHz


These variables could be used to modulate the shepard, I'll hook up some pots the next time I'm in my studio.
Quote:
float phaseIncrement = kControlRateScale / 40; // 40s sweep
uint8_t numSines = 8; // 1..8;
float phaseShift = 0; // phase shift in semitones
float intervalSemi = 12; // interval spacing in semitones
float centerNote = 72; // not of mid sine


BTW is there a better way to post code blobs than to use quote tags?

Reality Checkpoint
loki wrote:
To hear a musical use of Shepard's tones go to YouTube and listen to Jean Claude Risset's Suite for Little Boy. It dates all the way back to the sixties and was generated on computer at Bell Labs.


Fantastic! Just bought the album!
cackland
andrewF wrote:
You can do Shepard tones, or something like them, with a frequency shifter. J.Haible described how to do it with his design, can't remember if it was here or on electro-music.

An easier option, I'm releasing a 12 hour sloth in a couple of weeks which will put out voltages that slowly rise or fall over a 4-6 hour period and cover 1-3 volts. It won't be an illusion, that pitch is really rising or falling and it definitely makes you tense hihi


Interested to hear more about this Andrew
Reality Checkpoint
lacsap wrote:
this evening I found some time to fiddle together some code to have a basic shepard tone on a teensy 3.2.


Thank you for your work on this. I shall be following your progress with great interest.
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