How to build a polyphonic theremin!

Hello, how are you all?
Well I am a student from Venezuela, trying to graduate on telecomunnication's engineering. So far I am doing good, but for the next month I have to make a polyphonic theremin. I have looked for some info on the internet but I haven't been able to find much.
If you know any website that could help me in the creation of a polyphonic theremin, could you be so kind in letting me know about it please?
Thank you very much!
be well!

Hi there, Vanegm. Welcome to Theremin World.

You're going to have to explain what you mean by a polyphonic theremin.

I understand that polyphony, in the sense applied to electronic instruments, means "able to play two or more unrelated notes at the same time" - which is a difficult thing for a theremin player to do as it requires both hands to control the pitch and volume of a single note.

"but for the next month I have to make a polyphonic theremin."

Ok - I have a question.. did someone instruct you to do this project, or did you choose it yourself? .. If you have been given this project (by lecturer or moderator or whatever) then I advise you to challenge it, and demand a different task.. If you chose this project yourself, you made a mistake! Try to change it!!

Even producing two simultaneous tones from a Theremin is a challenge.. Building a truly polyphonic Theremin may be impossible, and is certainly impossible if the instrument is a 'true' Theremin with antenna for volume control.. As Gordon said - playing it could pose problems!

The only way that I can see would be to have a multi-axis Theremin (http://www.epsilonsynth.com/home)which leaves a hand free to play some other controller, for example a keyboard.. But Epsilon is still in development, and, even having developed Epsilon this far, I would not take on the task of adding polyphony for a one (or even three) month deadline.

I am slow.. so you might do it quicker.. But if you managed to build any kind of polyphonic Theremin in one month,well, I would eat my hat (if I had one!)

Dont think you will find what you are looking for on the www .. I dont know of any polyphonic Theremins.. The closest you might get is a Theremin controller (I think Doepfer do one) which gives a voltage output you could use to drive analogue synth modules, or one of MIDI (PSoC based) Theremin controllers.. but you wont get schematics for these, and you dont have time to gut them.. And they will still not enable you to build a true polyphonic Theremin.

I've been thinking some more.

What does "theremin" mean in the context of this assignment? Does it mean "any proximity controlled musical device" or specifically the sort of instrument that thereminists use?

If it means "any proximity controlled musical device" then you could make a number of very small devices that each play a single pitch at a volume determined by the proximity of a finger, then line them up and call them "a theremin keyboard."

I would be inclined to produce five of them for single handed operation, tuned to a pentatonic scale so that any combination would sound harmonious, and with a soft timbre to make lovely drifting drones.

I think that an optical sensing system would be more achievable within the time available, and allow you to focus more on producing a good timbre or range of timbres, although an RF device might give a neat opportunity to try out FredM's novel Theremin Tone Generator that is being discussed in this thread: Thereminworld.com/forum.asp?cmd=p&T=3601&F=1 (http://www.Thereminworld.com/forum.asp?cmd=p&T=3601&F=1).

I have played a polyphonic theremin.

A number of years ago, a California inventor and theremin builder conceived a theremin with two entirely separate voices, both controlled by the pitch arm of the player.

Voice one was controlled in the same way as the conventional theremin with gestures toward and away from the pitch antenna. Voice two was controlled by lateral movement, to the left and to the right, of the pitch arm and the sound was generated in an entirely different way.

Since it was not feasible to have two totally independent heterodyne sounds being produced at once from the same electrostatic field, the second sound was produced by a tone generator and used an echolocation device (which did not in an way interfere with the the EM field for voice one) to identify the lateral movements of the pitch hand.

Volume was controlled in the traditional way and applied to both voices simultaneously.

The inventor of this instrument was anxious to have a precision thereminist try to master it and he sent me his prototype. After struggling with it for a couple of weeks, I decided it was not a viable musical instrument and returned it to its builder with my thanks.

Playing a single voice in the traditional manner is already difficult enough on the theremin. Playing TWO voices with anything even approaching precision, I found to be virtually impossible.

Los Angeles thereminist, Charles Richard Lester, also tried this polyphonic device and we agreed that as ingenious and creative as it was, it was simply not practical by any stretch of the imagination.

Leon Theremin built a polyphonic theremin but the secondary voices were not independent of the basic heterodyne sound. They were generated by a kind of analog harmonizer. There is a recording of this device made by Theremin himself.

coalport said:

“Leon Theremin built a polyphonic theremin but the secondary voices were not independent of the basic heterodyne sound. They were generated by a kind of analog harmonizer. There is a recording of this device made by Theremin himself.”

Interesting they all seem to be in California, I used the keywords “polyphonic theremin” in Google and Yahoo and at the very top of both lists was an interesting approach. This guy seems to have retired the project but interesting nothing the less.

The Ultermen a Polyphonic Theremin

http://www.oldtemecula.com/theremin/ultermen/ultermen5.htm

Christopher
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I can't comment on what is and isn't possible mechanically, only practically for the musician.

The problem is that a Thereminist, much like a mortal human, has two arms. Only one of these arms can control pitch. The other must control volume.

What you're attempting to do is add another string to an instrument which only has room for one. However, there is already another element interrupting the field, and that is the volume arm. This is the non-dominant arm and requires less precision (where the pitch arm must find notes from precise points in the air, the volume arm provides swells and fades). It is also arguable that - in sacrificing a degree of finesse - the hand of the volume arm could be allowed to move somewhat.

When one pictures a polyphonic theremin, one imagines that all perameters must be controlled by gesture. However, a Theremin could provide a second, harmonic tone, which would always relate to the first in semitones. So you could provide a controller for said tone.

What I'm thinking is a small device to be held in the volume hand. In order to vary the note, the user would compress or expand it, with the intensity of compression causing the note to drop by anything from 1 to 12 semitones.

Of course this would still be incredibly difficult to play, but I think it might be more feasible than attempting to add a second antenna, or even additional perameters for the pitch arm.

Also I'm just being theoretical here. I know no scientific basis for anything I've just said.

GordonC asks:"What does "theremin" mean in the context of this assignment? Does it mean "any proximity controlled musical device" or specifically the sort of instrument that thereminists use?"

I think that expanding the scope of the Theremin to include "any proximity controlled musical device" would be an error.. I do not regard Epsilon as a Theremin, but perhaps could say it was a Theremin related instrument.

Could an instrument which used some mechanism other than capacitance (optical or ultrasonics, for example) and behaved like a Theremin (had pitch and volume antennas) be rightfully called a Theremin?.. ie - If one had an instrument which looked like an EW, played like an EW, and sounded like an EW, but had completely different technology, be a Theremin? hmmm.. I dont know!

If the scope of the assignment includes any means of generating notes by proximity sensing, then a polyphonic "Theremin" is not only possible, but easy..

One could buy 12 PSoC proximity evaluation boards, use the PSoCs MDACs as VCA's, Have a single pitch antenna running at HF, with a HF reference and D-Latch 'mixer', build a top octave generator using HC74193 programmable dividers*, feed the 12 top octave signals (after simple RC filtering) to the 12 proximity boards (input to the MDAC), Sum (mix) the 12 MDAC output signals to get your polyphonic output. The volume for each 'key' would be determined by proximity to the key, and the master pitch determined by proximity to the pitch antenna.. It would be like having a keyboard with the pitch bender wired to a "Theremin" CV out..

You will need to place the 'keys' reasonably far apart, and have the sensitivity quite low, to have any chance of making it playable.. might need some clever key arrangement so that musically pleasant combinations are more likely when sensing fields overlap.

*this is a clumsy way of generating a top octave - I used it before top octave ICs were available - then they were manufactured making life for electronic organ builders much easier.. Then these ICs were discontinued, and the replacements could not handle wide range frequency input (I do not know if there are any TOS ICs still made).. I have a few of these rare IC's somewhere, and if you chose this route I could send you one to simplify things - you need all the help you can get! :)

I have just realised that you dont need a TOS.. The PSoC has sufficient resourses to allow each sensor to generate its own semitone reference from the pitch oscillator input - I will advise you on this if you need help.


Which is the other way to do this - build a polyphonic analogue (or even MIDI) synth, and take a pitch controlling output to it from a proximity sensor.

Whichever way you do it - 1 month? I will still eat my hat!

[i]I think that expanding the scope of the Theremin to include "any proximity controlled musical device" would be an error[/i]

I agree. I'm just trying to ascertain the scope of the project. A quick trip to eBay will illustrate that people use the word theremin quite loosely at times.

Hello! First of all thank you so much for all your help!
well let me put it this way, I think my teacher has no clue of what is he talking about. The thing is that this class is called radiations so it has to work with electromagnetic fields, so I can't work with optical sensors. He asked us to build a theremin but he said he wants something more creative than the regular theremin he sees on the web.. Now, here is why I think he has no clue about this: he told me, I want you guys to bring me something different, creative, not the regular theremin, it can be a polyphonic theremin!.. So he wants this project for november 17th, and that's why I think he's crazy. I prefer your opinnion guys on this matter, in telling me that a polyphonic theremmin is practically not posible!
But I still need to do a theremin, but something creative...but a theremin at last haha, and it has to work with radiations, so it cant be optical. Does anyone has any idea what it could be like?
Once again thank you very much for all your help. You guys are very smart and true gentlemen!