Moog Theremini Theremin

Let's Design and Build a (mostly) Digital Theremin!

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Posted: 8/17/2014 1:33:55 PM
FredM
From: Eastleigh, Hampshire, U.K.
Joined: 12/7/2007

threads posts

Hi dani -

Kitten ? A human "kitten" yeh ;-) ... As for it being a "geometric art", I agree - its the implementing of this in physical form (as in, knowing what can be obtained or easily bought or made, and what the best simple  design is that does the job)  thats my problem.. I would love someone to design a simple piston-action "virtual thereminist", and if you had any ideas on this, please share them! (perhaps this is worthy of continuing as a technical hijack?)

Fred.

Posted: 8/17/2014 1:46:50 PM
dewster
From: Northern NJ, USA
Joined: 2/17/2012

threads posts

If I were to make a linearity tester, I'd probably go the route of how I obtained capacitance data from my own hand / arm / body: have a non-conductive linear actuator with one end positioned near the midpoint of the pitch antenna and perpendicular to it, and the other end at the "shoulder" location.  From the moving part of the linear actuator hang a conductive sphere "hand", connected by a passive wrist joint to a conductive tube "forearm", connected by a passive elbow joint to a conductive tube "upper arm", connected by a passive shoulder joint to a conductive tube "body" and ground the mess.  So the hand would make linear movements to and from the antenna, and the arm elbow would naturally hang below.  No active complex joints or other robotic machinery required.

Posted: 8/17/2014 3:17:10 PM
Touchless
From: Tucson, AZ USA
Joined: 2/26/2011

threads posts

Dewster I think by your nature you overcomplicate things but that got me to thinking about the time that I had a theremin setup next to a grandfather clock and the pendulum was slightly playing the theremin. Being on a budget and reading your description I think a grounded long wire pendulum wire attached overhead would be a straight-line movement using a predetermined sphere/surface at the bottom like a coke can. Have it swing 3” off the side of the pitch antenna back and forth. The highest speed would be the higher musical pitch and the slowest the lowest or Null where the direction changes. It might audibly reveal with the arch of the movement and the swinging whoop sound, something observable about the pitch field.

T

Posted: 8/17/2014 4:24:00 PM
dewster
From: Northern NJ, USA
Joined: 2/17/2012

threads posts

"Being on a budget and reading your description I think a grounded long wire pendulum wire attached overhead would be a straight-line movement using a predetermined sphere/surface at the bottom like a coke can. Have it swing 3” off the side of the pitch antenna back and forth. The highest speed would be the higher musical pitch and the slowest the lowest or Null where the direction changes. It might audibly reveal with the arch of the movement and the swinging whoop sound, something observable about the pitch field."  - Touchless

That would work great for finding quantized / sticky pitch.  But you might have a hard time getting it to oscillate at ~1kHz to find F3 of the response time! 

A small toy DC motor with a wire (and a flywheel if smoothing is necessary) hooked up to a variable power supply would likely work fine for both types of measurements.

Posted: 8/17/2014 7:36:49 PM
xtheremin8
From: zurich
Joined: 3/15/2014

threads posts

maybe it's already beating a dead horse.  but i'll post it anyway.

a arm-solution (could be made off a salvaged lab-lamp).:http://www.google.com/patents/EP1603712B1?cl=de

and another linear approach.: http://www.youtube.com/watch?v=9qu1uOB-9jQ

i'm courious of what you built finally, but i won't interfere this topic anymore.

fred: Kitten ? A human "kitten" yeh ;-)  no, meant that from the video, soloing on a gakken! 

Posted: 8/19/2014 2:40:48 PM
dewster
From: Northern NJ, USA
Joined: 2/17/2012

threads posts

http://www.mediafire.com/download/b6h2dgq86i8d1jk/Offset_Heterodyne_2014-08-19.xls

Updated the quickie spreadsheet a bit and added an offset to the numeric offset.  I believe I now understand why the UNO SW does this (the "+200"):

     case 4: add_val=(pitch_init-pitch_v)/2+200; break; // normal operation

The numeric offset helps to linearize the far field.  Small offsets like this have much more effect on the far field as the numeric change is smaller there.

I also removed the polynomial linearization factor.  The UNO approach seems quite linear enough without it, and can be adjusted via the operating parameters ("Beat Minimum" and "Numeric Minimum" in the spreadsheet).  I'm hoping the user linearity adjustment will be "twist the knob to the point where the pitch doesn't drop as your hand approaches and touches the antenna" or something similarly simple, and with a far field tweak for inveterate tweakers.

The numeric "Center", "Sensitivity", and "Octave" tilt and translate the resulting response.  It is my dream that adjusting these controls will enable Thereminists to use more exaggerated movements, and therefore relax a bit more when playing.

Posted: 8/21/2014 12:02:43 AM
RoyP
From: Scotland
Joined: 9/27/2012

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Aye, so I’m here just watching some repeat crap film on the telly when I had a rush of blood to the head and thought I’d post it here on TW, somewhere.
I hope this is the right forum...
I’ve been thinking a wee bit about the Theremini and wondered at it’s pitch correction as a means to aid (or not) learning to play the instrument.
I got to thinking what would make a learning aid and came upon the idea of a volume spike.
I’m sure that I’m not the first person to think of this but this thread is HUGE with LOTS of pages and, to my shame, I’ve not really been following it.
The idea is pretty simple.
Have a practice setting where the theremin acts as a pitch only and have notes in the scale present themselves louder than the off-notes.
So for example you would have a scale from C-àC’ with the notes in between

C—D—E—F—G—A—B—C’

If the normal volume was, say, V, then as you went up the scale the notes would play thus:

C(V*4)—D(V*2)—E(V*2)—F(V*2)—G(V*2)—A(V*2)—B(V*2)—C’(V*4) etc etc etc

The volume spike wouldn’t be just on or off like a square wave but would be more of the positive half of a sine wave where the perfect pitch would be at the apex. Maybe a saw wave shape.

Possibly there would be an adjustment to correct the width of the peak so that it could be tuned for extreme accuracy or a floppy accuracy. I’m sure you know what I’m getting at here.

Like I said, this has probably been suggested before.

Ok, going back to a darkened room now...

R

Posted: 8/21/2014 12:42:28 AM
Touchless
From: Tucson, AZ USA
Joined: 2/26/2011

threads posts

Roy you made me laugh and I like your creativity. IMHO theremin playing is too fast so the circuitry would probably not be able to process and keep up. Your idea is good but I think it would cause a zipper effect. It gets back to my example of the guy doing pushups in the other thread. The dewey theremin might do it though. (-'

The original theremin is perfect, all we can do is imitate. Can perfection be improved?

T

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