# Odd question: Pitch antenna design ...

Posted: 7/20/2012 4:40:39 PM

From: In between the Pitch and Volume hand ~ New England

Joined: 12/17/2010

Well, don't ask me why I always come with weird things when I take a bath... It's the time where I come up with melodies, lyrics and creativity... Who knows lol.

... But, I was thinking of a new design for the theremin, and mostly it has to do with the pitch antenna. Pardon my noviceness here and if it has been discussed, please just politely tell me to shut my pie hole...

Right now, when we play the theremin, closer to the pitch rod we obtain highest pitches and the further away from it (towards our body), we obtain lowest pitches. How about from the top part of the antenna we get the highest pitches while when we slide the hand toward the bottom we get to the lower pitches?

this way, you could drop the height of the theremin to access the pitches/note range needed for a piece and it would be beneficial to hand stability since it would be closer to our body instead of being away from it...

Am I making sense?

Posted: 7/20/2012 5:49:31 PM

From: 60 mi. N of San Diego CA

Joined: 2/15/2005

Hello Amey,

This is a creative idea, I like to  think of myself as a specialist in theremin adaptation. The theremins basic response occurs from the distance of the closest grounding mass to any part of the pitch antenna. All the fancy finger work you see many thereminist doing is still just to set the distance from the forward point on their hand to the antenna.

The human arm works most natural with a forward and back motion, for stability try sitting in a chair, this gets rid of bobbin and weaving.

Only workable approach: As you know the pitch field can be easily reversed and so to have the lowest note highest over your head the antenna would also need to be up there horizontal to the ceiling. Lowering your hand to the top of your head would be the highest note. From the top of your head to the horizontal antenna above would determine the width of the pitch field. You could mount a vertical wood dowel in front of you so you have reference to something and mark the upper section overhead with the note intervals of your theremin design. My arm is already getting tired.

Edit: OK I had lunch so now I can think. In the above paragraph you would not need to reverse the pitch field, everything else looks good. If you stood on the ground side of the horizontal antenna you could lower it to be more in front of you. This would be a good experiment as it might make playing more intuitive but you would lose arial fingering.

I think for the best stability playing a standard theremin is sitting in a chair with wooden armrests and possibly resting your elbow would be an approach to try.

Now thereminists will chime in and say resting an arm on the chair while playing theremin is like putting your elbow on the table while you eat. Both will add limitations but a theremin won't poke you with a fork.

Christopher

Posted: 7/20/2012 5:58:16 PM

From: In between the Pitch and Volume hand ~ New England

Joined: 12/17/2010

no need to sit... just bring the theremin down some so that the highest note on the antenna is at your shoulder level and the lowest one at your hip (there wouldn't be a need to rest your arm at all)... there would be a different technique involved for certain. I think it might tire less the arm to keep it close to you rather than forward away from you without resting.

Posted: 7/21/2012 12:17:06 AM

Joined: 8/1/2008

Amey: "How about from the top part of the antenna we get the highest pitches while when we slide the hand toward the bottom we get to the lower pitches?"

Plate antennas work in this way.

Rather than a rod & ring, the pitch and volume antennas consist of two flat horizontal plates - one on either side of the instrument. Control is accomplished by moving the hands up and down 90 degrees perpendicular to the plate surfaces. (This is basically what you're describing only the "vertical" antenna is invisible).

I think Bob Moog came up with this innovation back in the 1950's or early 60's and theremin builder Art Harrison makes plate antenna instruments today. It's O.K. for experimentalists, aleatoric players and FXists but not good for precision playing. With the up & down motion, gravity is fighting you all the way reducing stamina and making accurate intonation far more difficult than it already is.

Posted: 7/21/2012 1:24:04 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

Amey,

Apart from the gravity aspect, there is also a problem with volume interaction - having volume control on a different axis to pitch control greatly reduces interaction between the two.. The pitch antenna does not "notice" up/down (Z-Axis or vertical) movement of either hand, and as the volume hand primarily operates on this axis, one does not get much interference from movement of the volume hand.

If both antennas operated on the same axis, the player would need to adjust their pitch hand whenever the volume hand was moved, just to keep the pitch constant - This, IMO, is a major disadvantage of plate antennas.

I do understand where you are coming from with regard to stability - but I think that this may be something of an illusion - The Z-Axis stability of the pitch hand does not affect the pitch.. so even if ones hand seems to 'wobble' a bit if your arm is tired, I doubt that this vertical 'wobble' will seriously impair playing (?)..

It is surprising to me to discover how much energy seems to be consumed by the pitch hand/arm when playing a theremin - I now get severe cardiac ectopics after a few minutes playing, but activities (like dancing with my kids) which I would have thought far more strenuous, I can now manage for far longer without any cardiac problems - This was the main reason I looked at a supportive "antenna in a box".

Fred.

ps.. "but a theremin wont poke you with a fork" - Christopher

ROFLMAO!  ;-)

Posted: 7/21/2012 1:43:04 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

"All the fancy finger work you see many thereminist doing is still just to set the distance from the forward point on their hand to the antenna." - Christopher

Chris,

The above is a long way from the whole story.. It is not only "distance from the forward point" which influences the capacitance / pitch, it is the total capacitance "seen" by the antenna.

Two major variables are at work to determine capacitance / pitch - they are distance AND area.

If you point your finger at the antenna with your fingertip at (say) a distance of 20cm, you will have (a lot) less capacitance (and therefore lower pitch) than if you moved a fisted hand to 20cm from the antenna

"All the fancy finger work" is about changing / controlling the capacitive distribution of the hand, and this comes down to combinations of distances and  antenna <-> hand 'overlap'  - it is highly complex and mathematically probably inscrutable, but thats what all the various techniques aim to achieve.

Fred.

"The theremins basic response occurs from the distance of the closest grounding mass to any part of the pitch antenna. " - Sorry, but this statement is incorrect, as can be shown with a thought experiment that can be tested.. take a 1m non-conductive dowel, and stick a thin single strand of wire (say <0.2mm diameter) along the length of the dowel, and connect one end of this wire to ground.

Now, holding the grounded end of the dowel, move the other end towards the theremins pitch antenna (holding the dowel horizontal) and observe the change in pitch.

Repeat the above with a ball of metal foil connected to the wire and attached to the antenna-side end of the dowel (or just move your hand to the same position ;-).

You will find that when one small grounded point (the diameter of the wire)  approaches the antenna, the pitch change will be marginal - if the area of that point (as in, with foil ball) is increased, there will be a proportional change in pitch for the same distances from the antenna.

The relationship is C= 8.854E-12 * A/D  .. The important thing to note is the relationship between plate overlap area A, and distance D.

Posted: 7/21/2012 3:09:10 AM

From: 60 mi. N of San Diego CA

Joined: 2/15/2005

Fred said: "The above is a long way from the whole story.. It is not only "distance from the forward point" which influences the capacitance / pitch, it is the total capacitance "seen" by the antenna."

After 10 years of 8 hour daily hands on research we will just have to agree to disagree.  In the beginning I tried to explain the genuine pitch field of the future and you keep falling back upon old school principles and the fancy math that fits your beliefs (facts) into the results you want to see. This is why intervention was necessary. (-'

Christopher

Edit: The old school I refer to is that the pitch fields Fred and I develop are very much different in the way they respond. The differences have been expressed numerous times in the past. It's too bad engineers are blind to this method I have demonstrated, as this hurts the theremin community.

Posted: 7/21/2012 11:03:23 AM

Joined: 8/1/2008

Fred said: "The above is a long way from the whole story.. It is not only "distance from the forward point" which influences the capacitance / pitch, it is the total capacitance "seen" by the antenna."

And then there are thereminists like me who play with their whole bodies!

I do not remain motionless when I play. I take a Tai Chi stance (legs apart, left leg back right leg forward) so that I can easily shift backward and forward when I play. I do not move my body when I am holding a note but I definitely move it for large interval leaps and when there is a rest in the music. I should also point out that I use a pitch preview so I can never lose my place in the static electric field. I always know exactly where I am pitch-wise.

When I built my first Big Briar Etherwave kit in 1996, I found that the linearity was extremely "pinched" in the higher octaves closest to the rod. This made accurate playing impossible in that register, and even the lightest vibrato became a "wobble" because the motion of my pitch hand encroached on the notes above and below. I found that by shifting my body very close to the antenna I could radically change the linearity, deaden the instrument's response, and make those upper notes much easier to play. I became accustomed to moving my body while playing and ear/hand muscle coordination became ear/hand/body coordination. My body shifting was included in my overall technique.

There is another important aspect of moving your body close to the pitch antenna when you are playing in the higher register. The closer your hand is to your body the more control you have over its movement. If you try to write your name with your hand at arm's length, you'll see right away what I mean. Theremin playing is all about CONTROL, and keeping your pitch hand as close as possible to your body gives you an enormous advantage for certain precision movements (particularly for vibrato depth and rate) and it is less stressful on the muscles and tendons of your pitch arm.

One other unexpected advantage of moving your body is that it also reduces stress on your lower limbs. Standing "frozen" and immobilized for long periods is not natural. Shifting your center of gravity back and forth as you play closer and further away from the pitch antenna increases circulation in the legs and greatly reduces tension.

Of course, non-precision thereminists don't have any of these problems and frequently move their bodies all over the place. For precision players, body movement must be carefully choreographed into the performance but, with practice, this quickly becomes automatic.

Posted: 7/21/2012 8:04:55 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

"The old school I refer to is that the pitch fields Fred and I develop are completely different in the way they respond. The differences have been expressed numerous times in the past. It's too bad engineers are blind to this method I have demonstrated many times, as this hurts the theremin community." - Christopher

Chris,

I really thought we had got over "nature of the pitch field" argument, and if, after "10 years of 8 hour daily hands on research" you have not seen that there is more to the pitch than just the distance to the nearest ground point, well - we either live in different universes where the fundamental charactaristics are different, or I am at a complete loss as to how you have observed what you claim to have observed, and how you have drawn the conclusions you have come to.

Usually, when I make a statement, I prefix it with IMO - Certainty is not something I am comfortable with.. But on this matter there is no "IMO" - Regardless of the mechanism (I am sure the mechanism is capacitive - but that is almost irrelevant) the effect of AREA AND DISTANCE on pitch  can be demonstrated - Try the experiment I detailed in my last post - I will bet everything I own that a small grounded point at any distance from the pitch antenna will have less effect on the pitch than a larger grounded point at the same distance.

In Peters last post he gave a clear description of how pitch can be altered by changing body position - I have seen Lydia use this method - I believe the reason this works is due to the TOTAL capacitance "seen" by the antenna determining the pitch - But even if capacitance was not the mechanism, the effect is real, and the capacitance "hypothesis" fully explains what is actually observable.

Maths? There really need not be any to understand this, but simply multiplying a (changing) fraction by a constant isnt "maths" its simple arithmetic. One could take any instant that a theremin is being played, and analyse the distance and area of every ground point reletive to the antenna, and from this accurately compute what the pitch would be - every point would return a value, and summing all these values would give total capacitance (or "whatever" if not capacitance) seen.

"It's too bad engineers are blind to this method I have demonstrated many times" What has any of this to do with "method"? If you were right, and the pitch was determined soley by the closest ground point to the antenna, then the theremin would be even less playable than it is in the universe I inhabit, where both area and distance (ie total capacitance) determines the pitch.

I am truly sorry that I expressed my disagreement with your statements - But (being who I am for better or worse) I had no choice but to do so. I do not believe it helps anyone to play the theremin if their fundamental understanding of the mechanisms are wrong - as, if anything " hurts the theremin community" this does - Also, I am passionate about science, and feel compelled to challenge blatant errors when they appear, If this comes over as a personal "attack" I am truly sorry.

Fred.

Posted: 7/21/2012 8:34:39 PM

From: 60 mi. N of San Diego CA

Joined: 2/15/2005

"The old school I refer to is that the pitch fields Fred and I develop are completely different in the way they respond. The differences have been expressed numerous times in the past. It's too bad engineers are blind to this method I have demonstrated many times, as this hurts the theremin community." - Christopher

OK, I changed the word completely which was exaggerated to very much different. I never brought up how the pitch field works, that's an exaggeration on your part.

So I will: When it comes to pitch antennas I refer to it as a transfer of energy or current flow in the antenna where by you refer to it as capacitance effect. Now I don't disagree with you, I have always said there was more involved.

Seems you used the same words when I referred to a forward point, I never said how broad the forward point was.

This reminds me of the current theory vs. electron flow, they are variations of the same school of thought.

Better yet Baptists vs. Catholics.

LOL

Now can we agree to disagree?

Christopher

Edit: Fred I apologize, I was not referring to you when I said this general statement, "It's too bad engineers are blind to this method I have demonstrated, as this hurts the theremin community."