# Moog Theremini Owners

Posted: 10/18/2014 9:52:56 PM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as WaveCrafter.com . ...................................

Joined: 12/7/2007

"note locations were nearly the same for both antennas. " - Gary

Once again, I think it likely that the geometry of capacitive fields may be giving different apparent results for different situations.. I think that Rich'es playing style and biasing may make the effect of a longer antenna more significant - Your fixed position box at the bottom of the antenna probably has less effect.

A longer antenna will give more angular capacitive coupling to the players arm, whereas a shorter antenna's capacitive coupling will prediminate more on the horizontal hand-antenna axis.

IMO, this usually gives better linearity for longer antennas - capacitance change as the hand approaches the antenna is somewhat less abrupt because there is a greater angular component which changes with a different law to the straight inverse-square law one would get if the hand was aproaching a plate.. Also, I think longer antennas could improve sensitivity in the far field.  I am not able to formulate any maths equasions for any of this, my maths skills aint up to that, so I may be talkning out my arse...

BUT - If there is any validity in the above, then I suspect that moving the hand / arm at the bottom end of the antenna (where the arm is closer to bulk ground capacitance and therefore has less coupling significance) then the improvement in linearity is greatly reduced.

I suspect that best linearity improvement (if it exists) would be obtained if the hand / arm was moved horizontally towards the centre of the antenna. I have drawn scale diagrams and tried to determine the effects of length and position with simple maths, and I think the best results would be with an antenna of twice the total length of the outstretched arm, with the arm moving on a horizontal plane to the centre of this antenna.. The best antenna to implement linearity would be a archery bow shape with the 'string side' facing the player..

Alternatively, one could just design the theremins electronics to give usable linearity... IMO, its not primarily linearity that makes the toy impossible to play, worrying about theremini linearity is really straining at the gnat while swallowing a camel! ..  ;-)

Fred.

Posted: 10/18/2014 10:44:03 PM

From: Sugarloaf, PA

Joined: 10/17/2014

Thanks Fred,

I wondered if the differences in note separation for both antennas were because of my hand and arm being located in a plane near the base of the antenna. What you said makes sense since the longer antenna would "see" more of my arm as I moved my hand closer.

I'll have to retest with my arm moving in a plane near the middle of the antennas.

Gary

Posted: 10/19/2014 12:31:59 AM

From: Northern NJ, USA

Joined: 2/17/2012

"I don't have a way to measure the linearity between using both antennas. Can anyone suggest a method?"  - Gary

Since the Theremini has a pitch display it's pretty easy.  Place your hand open somewhere near the antenna, fingers pointing at it, and move your hand in and out until you hit a particular arbitrary pitch, for the sake of argument say C6.  Close your fingers into a fist and see what the change in notes is.  Then open your hand again somewhat farther away and position it until you get C5 (an octave lower) close it to see what the change in notes is.  Continue doing this until the pitch response poops out.  You can get an intuitive feel for pitch linearity this way.  To make it easier you might want to adjust the high / low pitch limits (not the calibration limits) to make roughly an octave difference between open hand and fist maybe 1' away from the antenna (the "midfield") and see how this changes nearer and farther from the antenna.  Play around with calibration distances (and maybe antenna length) to see if you can expand the linear midfield.

As Fred points out, you probably want to position the Theremini height and your body so that your hand is moving in and out on a line roughly perpendicular to the center of the pitch antenna, your elbow pointing at the ground.

It's fairly complex mathematics working in your favor when it all falls into place, and working against you otherwise.

Posted: 10/19/2014 12:44:09 AM

From: Sugarloaf, PA

Joined: 10/17/2014

So I just did a retest of both antennas.  I tied kite string around the center of each antenna and tied the other end to a camera tripod.  Using a string is something Coalport had suggested. I kept my hand level on top of the string. For the 20" replacement antenna I marked the location of notes on the string in black magic marker.  For the original antenna I marked the notes on the string with a red marker.  I recalibrated the Theremini each time I swapped antennas.  What I found was similar to my earlier results, when I moved my hand in a plane near the bottom of the antenna.  The distance between notes were slightly larger with the longer (20") antenna when I got closer to the antenna at a higher pitch.  So, I guess that means using the longer antenna improves the linearity a little.

I'll try adding a photo of the string setup below, but it is difficult to see the red marks on the string.

Gary

Posted: 10/19/2014 2:06:30 AM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as WaveCrafter.com . ...................................

Joined: 12/7/2007

Gary,

First, I must say that this is interesting for me - but on a purely academic level.. The theremini is probably the most useful thing for this kind of static measurement (There! I said something good about it! ;-)

It took me years to accept the huge complexity involved with precision theremin operation and playing - "wasted" years where I completely under estimated the difficulties - and I was an EE with 40+ years behind me, and for several of these I was involved in short-range precision capacitive sensing, and I still didnt "get it" for a long time... I do get agitated when I see others making the same mistakes I did, I want to help them and to warn them - But when I see engineers who have access to all the priceless data left by Bob Moog making these same (or worse) mistakes, agitation morphs into rage, and I go passionately OTT !

Your mechanical methods are interesting and add to a pile of data - but you are trying to quantify something that cannot be quantified without far superior resources - do the tests tomorrow and if humidity has changed or anything in your room has moved, and the results will be different... Get someone else with different body mass or hand size or whatever to do the tests, and the results will be different.. Angle the string more towards the baguette, and the results will be different.

One thing though is that the results you have shown are a lot better than I had expected.. Oh, they are bad.. but not bad enough to be the reason that nobody has yet been seen doing a listenable musical performance on the theremini.

Your star trek performance, even with the 50c error, was about as good as anything I have heard in unquantized mode.. and I believe the reason for this is that you were effectively using your cheat sheet as a "keyboard" - you were moving your hand to a marked position where you believed the note was right, and not correcting the position to compensate for what you heard.

And perhaps this is the only way to play tunes on a theremini.. Have a keyboard wired to a bunch of adjustable capacitors (twisted pieces of wire for example) tuned to give semitone intervals, and play this - slowly.. The thereminis natural portamento will do the rest - and you could even have a small exposed bit of antenna you could use for (slow) modulation (except youd need three hands )-:

Fred.

Posted: 10/19/2014 3:23:12 AM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as WaveCrafter.com . ...................................

Joined: 12/7/2007

What I am about toexplore in the following is intended to be helpful - you can believe that or otherwise, I truly dont care!

If one is going to use the theremini, IMO, from the perspective of engineering / science, the first thing to do is establish what is physically impossible.. Then perhaps to establish what is musically practical.

It may also be worth looking at what playing habits could possibly be changed, and what possible "adaption" the brain might make (learning / subconscious 'programming') to facilitate exploiting the thing.

1.) We know with  certainty that any sequence of 10 notes can not be played within one second - at 100ms, no note would hit the key.. We can probably say that the fastest sequence that could be played, with enough time for the note to settle on an interval, will be 5 intervals per second or less.

2.) I have been thinking that lack of real-time feedback absolutely made the thing unplayable - but am I under estimating the ability of the brain to subconsciously learn? If the brain can learn the portamento "pattern", is it possible that the compensation loop could cater for this, and the player could avoid 'oscillation' given enough time / practice / programming ?

I have my doubts about the above - but not enough knowledge or understanding on the matter.. My statements like "impossible" and "absolutely" that I made before MIGHT be a bit rash .. Doesnt change my opinion of the thing or its designers though - Even if possible, (which I doubt) its not needed or wanted.

3.) If one takes (1) as true, then modulation at a frequency in excess of about 5hz or lower will not be under control of the player in any normal way.

Dewster was mentioning flight simulators and operator oscillation in the other theremini thread..

I wonder if any techniques were developed back in those days of slow PC's which could be applied to playing the theremini?

Fred.

Posted: 10/19/2014 11:10:18 AM

Joined: 8/1/2008

Fred, let's say it is possible for the human brain, given enough "time / practice / programming" to compensate for the design shortcomings of the Moog THEREMINI. It seems to me that the effort would be wasted because whatever had been learned could not be applied to playing any theremin other than the THEREMINI.

I'm feeling a little sorry for "SapereAude" who started this thread in the hope that it would not turn negative and end up chasing him away. I fear that it has done just that!

I still believe that something very cool can be done on the THEREMINI.

"First, have music in your soul. If you have THAT, you will find a way to do it." Clara Rockmore

Posted: 10/19/2014 12:38:13 PM

From: Northern NJ, USA

Joined: 7/29/2014

I totally agree that something very cool can and will be done with the Theremini and hopefully I'm going to be one of the ones doing it.

So here's the call to all you proud Theremini owners like me - STOP MEASURING IT AND START PLAYING IT!

And I'd love to hear any of the music you Thereminiists come up with.

Rich

Posted: 10/19/2014 12:38:54 PM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as WaveCrafter.com . ...................................

Joined: 12/7/2007

"I'm feeling a little sorry for "SapereAude" who started this thread in the hope that it would not turn negative and end up chasing him away. I fear that it has done just that!" - Coalport

It may have.

But isnt that his "problem" if this is the case? I dont see any post here as "negative", or any post which  argues against "something very cool can be done on the THEREMINI"

My first entry on this thread, (which I had intended to avoid), was to Gary - it was because Gary was talking in terms of playing the theremini like a theremin, that I advised him to get rid of his theremini and get a theremin.

And this, to me, is what the whole matter rests on - there is no point in thinking about the theremini as if its some kind of theremin that can be played as a theremin - and as you rightly say: " It seems to me that the effort would be wasted because whatever had been learned could not be applied to playing any theremin other than the THEREMINI." even if you did manage this to some degree after expending a load of effort.

And in the light of the above, IMO, theremini owners interests are not served by staying silent here - those who play and / or understand the limitations of the theremini are the ONLY ones able to advise them on directions which are pointless, and things they CANNOT do with it.

And if "we" stay away from this thread, then one gets a thread which fills with useless biased information - a thread that serves nobody's interests (other than perhaps Moog's) and which becomes yet another misleading place on the WWW where potential theremini purchasers are misled.

With full knowledge and analysis of the theremini's faults and limitations, and discussion about its possible musical uses bearing these limitations in mind, this thread could actually serve a useful function for theremini owners IMO.

But IMO this thread can only be useful to anyone if the TRUTH about the theremini's limitations are on the table and referenced against anything folks propose to do with the theremini.. Saying nothing about Gary's first post and pretending that a cheat sheet was a solution would not have served anyones interests.. If Gary wants to play star trek and other tunes, my advice that he sells the theremini and buys a Moog EW is still the best advice - and if saying that chases away someone, then IMO, so be it!

Fred.

Posted: 10/19/2014 4:41:56 PM

From: 60 mi. N of San Diego CA

Joined: 2/15/2005

Fred said: " my advice that he sells the theremini and buys a Moog EW is still the best advice - and if saying that chases away someone, then IMO, so be it!"

This thread is for Theremini owners to express fun and adventure in their new purchase, not self proclaimed experts in all things electronic, that is why I have mostly stayed away. People that are new to Theremin World need to feel welcomed and not trampled upon. Hijackers and Trolls are not welcomed.

Christopher