Ethervox MIDI Theremin

Hey Fred,

what I forgot to ask you, to build a simple Circuit which produces a Frequency (omitting the variable oscillator), Would it be possible to build it with the parts I have in the plan? Would the Armstrong-Circuit be a good choice?

Sincerely,

Alex

OT  - Note for other forum users:

This thread is NOT about the Moog Ether-Vox!

Hello Alex,

If you want a theremin, you need both oscillators -

I will look at the components you have, and see if I can salvage your situation an provide a circuit with a better chance of working.. keep tuned, I will post it here..

Fred.

ok - have a look at this : http://www.thereminworld.com/epe-simple-theremin-project

and specifically this from the above: http://www.thereminworld.com/pics/articles/epemag/PAGE2.JPG

At least your 100uH are usable, as are your transistors.

I dont have time right now to design and simulate something using more of your components.. Might have time late tonight or tomorrow... But in the meantime read the article above and try to comprehend as much as you can - the more you understand, the better your chance of getting something working!

Untested - based on Andrey Smirnov's theremin circuits http://theremln.ru/asmir/tsensors_sch.htm, this may just save your circuit:

THIS IS A SALVAGE EXERCISE! - PLEASE DO NOT ATTEMPT TO BUILD THIS CIRCUIT UNLESS YOUR BACK IS UP AGAINST THE WALL! - THERE IS NO WARRANTY THAT IT WILL WORK AT ALL, IT HAS NOT BEEN SIMULATED, AND IF YOU WANT TO BUILD A CIRCUIT LIKE THIS CHECK OUT ANDREY SMIRNOV'S SITE FIRST!  - THIS IS A DESIGN EXCLUSIVELY FOR ALEX TO TRY TO SALVAGE HIS PROJECT!

(even so, it is still a better circuit than the original Alex presented here)

I WOULD NOT USE THIS DESIGN! - IT NEEDS BIGGER INDUCTORS UNLESS USED WITH AN ANTENNA INDUCTOR, AND IS FAR FROM A GOOD DESIGN FOR ANY DIRECT_TO_ANTENNA THEREMIN!

SMIRNOV INTENDED HIS DESIGNS TO BE USED WITH A SERIES ANTENNA INDUCTOR.

 Reduce R10 and / or C11 for more harmonics, may need to reduce or remove C12 and C13 for more signal level and harmonics. Audio output needs to to go via a big capacitor (say 47uF) to an amplifier, ideally via a buffer amplifier.. perhaps your spare transistor..

I changed C4 and C8 values to make the oscillators more sensitive and to keep them to values you have, but they are specified at 1n2 (1200pF) by Smirnov, and may need to be changed.

If you can get the circuit to work at all on your horrible plug board, you may need to put a tuning preset potentiometer on the variable oscillator as well as the fixed oscillator (both oscillators are identical apart from this) as you will probably need all the adjustment you can get..

You will at least need an oscilloscope, but probably also a frequency counter.. look at waveforms on the emitters NOT the collectors, as probes on the collectors will change everything!

"So, you couldn't help me further with the circuit? (it's just I need to know how to proceed further with the presentation)" - Alex

I cannot help you to get your present circuit to work, but there is a slight chance you could use those components to make something that changes its pitch as you move your hand..

"But what I want to know is, how the sound (lets say a sine wave), coming from a theremin, is filtered in real time. Can it make the theremin sound like the violin in real time?"

First - if you filter a sine wave, the most you can do is reduce (or if the filter has gain, increase) its amplitude - you cannot modify its harmonics (overtone) levels, because a sine wave has no harmonics.

With subtractive synthesis, one starts with a waveform rich in harmonics, and removes (or reduces or increases) the harmonics you want to alter.

As to "Can it make the theremin sound like the violin in real time?" - my first post here answered that question I think, and the SOS articles elaborate - IMO the answer is both "yes" and "no" - One well never get a good emulation of a good violin played by a master, even by a master thereminist with a good instrument - Acoustic instruments just have too many factors which make each unique - even "physical modeling" cannot produce a convincing Strad (or even a specific cheap violin).

All that can be done is to get an proximately "right" tone and play the "emulating instrument" as closely to the form of the 'original' instrument - if these conditions are met (or reasonably good enough) it may fool a non-critical listener.

But this brings me to a question perhaps you should raise in your presentation... Is there REALLY any point in trying to emulate an acoustic instrument accurately on a theremin? The obsession with "emulation" arose, I believe, at a time when peoples imaginations were limited to the sounds from available acoustic instruments - those days are passed -

Ok - the idea of a "universal" instrument that can replace acoustic ones is tempting - and can almost be realized IF one isn't trying to exactly copy another instrument.. But someone who REALLY wants to play and master a violin (and I am talking about REALLY wanting violin - not just a violin-like sound) should get a violin , not a theremin!

Bowed instruments are generally more difficult to emulate because of the control the player has over pitch and dynamics - For this reason the theremin is better suited to emulating the violin than say a keyboard.. But after many decades of trying to emulate the sound of an acoustic grand, and with millions of £ spent on R+D, we are only getting close to a reasonable replication now.. There has been no such effort devoted to using the theremin to emulate bowed instruments (IMO for good reason ;-) and we are millions of miles from getting to the point that a theremin could realistically perform such emulation for a violin IMO, and I would bet it wont ever happen.

If the sound and playing fits the music, isn't this all that matters? If the listener thinks "this sounds like a violin" or "this sounds like a theremin" does it matter? - surely all that matters is whether its enjoyable / musical / expressive.. If its not, if it needs a real violin sound for whatever reason, then something is "wrong" - and this "wrongness" probably wont be primarily due to the sound from the instrument, it will be due to the playing or use of a theremin for that part.

To me, the beauty of electronic instruments is the ability to 'sculpt' the sound to suit the part - Lev Theremin was, I think, not thinking this way with the theremin - And rather than accepting their place as synthesizers, theremins have retained limited tone and synthesis control built into them.. Its a bit like if Bob Moog had simply picked a few presets and given user control of say decay time and filter cut-off.. this would have limited the potential - Only a fool would attempt to emulate a grand piano on a Mini Moog - but thats not what musicians want to do with it! - Theremins "should" be recognized as monophonic synthesizers, its only the fact that they have been artificially "disabled" that has caused them to be seen as something other than synthesisers. (I suspect that one reason modern theremins have retained this limited adjustment of tone is because its cheaper than bringing the theremin to "standard" and people seem to accept these limitations so there is no motivation for change)

If they had not been "disabled" then the question "Can it make the theremin sound like the violin in real time?" Would be similar to asking whether a Mini-Moog and a ribbon controller could sound like a violin.. and the answer would be that with the ribbon controller it was  better suited, but still not able to do a truly realistic 'emulation'.

Fred.

Have you seen this http://www.thereminworld.com/Article/14388/new-theremin-cello-video-online ?

Doesnt sound like a Cello to me!  But thats OK!

Hey, Fred,

First of all, before continuing, i feel that I have to say thank you so far, because you give me some hope that the presentation couldnt turn out too bad. :)

What I want to clarify here is that by asking the question "if the theremin can emulate a violin", I already came to the conclusion that it is rather very hard/impossible. But somehow I need to underpin my conclusion with facts. What are the possibilities so far? So there is physical modelling, for example. What does it exactly do? Could it be applied on a theremin? Can some sort of a subtractive synthesis be applied to a sine wave by firstly adding all the harmonics and then subtracting the right ones?

I must stress that in high school here (Germany), my teachers would be more than satisfied with seeing how this idea could be potentially solved - and this very concise. And the good thing is that I dont have to consider all possible playing techniques like pizzicato etc. I will just say that this is way beyond today's technology, just by seeing how hard it is to simulate even a simple way of playing. I just want to concentrate on a single violin string bowed in a typical way. Slowly. Just like Pamela Curstin in this TED Presentation (which is actually quite nice): http://www.ted.com/talks/view/lang/en//id/218 Here she only plays a "simple" solo.

She even imitates a bass plucking.  In fact, this "violin" sound is not really close, but explaining how such a sound could be produced on a theremin would fulfill my teachers expectations for sure. But there she plays on a MIDI theremin...

I thought that it would be best to talk about both ways of solving the problem, the "MIDI-one" and the one I asked you so far. It is not bad if it isnt authentic. In fact, your final paragraphs are likely to this I planned to say at the end, but you formulated it quite good. :)

Sincerely,

Alex

Fred, your link towards Valeria Sturba playing a theremincello (housing by Augusto Triani, circuit by Alessandro Pierotti) is perhaps not a good example.

You may find here Marieke van der Heyden (a professional cellist) playing a different theremincello (housing still by Augusto Triani, but with a different circuit, developed by me). I think that the sound is much closer to a real cello than in the previous example...

Hello,

wow... this is pretty impressive, Thierry.. This sounds really authentic.. Is it a big secret how you made it? :-) I would just like to know generally what you did, if thats okay.Is this a theremin where the antennas are replaced with the special kind of neck? How did you change the sound of it? I mean what did you do to approximate the cello sound?

Btw., I just realized that a theremin doesn't have just a sine wave but a plethora of overtones. Here is an extract of this sample: http://www.thereminvox.com/filemanager/download/35/wave_control.mp3

Here is a spectrum of a violin:

Could be still applied a subtraction synthesis? What devices would be needed to filter it? Can a filter bank do this in real time?

Sincerely,

Alex

Hi Thierry,

Yes - much more like a cello at some pitches (perhaps its the poor recording quality, but it sounds far more cello-like away from the bass IMO - The mid registers are qiote convincing though)

I didnt really go looking for theremin cello's (just cliched the first video link in a TW search) - just pointed at it to show Alex that they exist, if he didnt know.. Lets face it, the "theremin cello" is nothing comparable to a theremin anyway - it uses a ribbon controller and entirely different technology.. a bit perhaps like what one could get from a Mini-Moog and ribbon controller.

But what are your thoughts on using a theremin to emulate a violin?

Hey Alex ;-)

I think it was a bad idea of mine to mention the theremin cello, as it has nothing to do with the theremin! - its completely different technology! - there are no "antennas".. Its only called a "Theremin Cello" because Leon Theremin invented it.

At a hypothetical level, an instrument using the "theremin" playing interface could probably be engineered to give a reasonable violin "replication" .. The key, IMO, is that the freedom of the player to control almost all aspects of pitch and dynamics may enable this better than some other player interfaces.

Physical modeling would, IMO, be the best way to achieve a bowed instrument tone - Physical modeling is a bit like real-time simulation of an electronic circuit - except it models physical components (strings, bridge, resonators, exciter) and actually "builds" a working representation of a complete instrument - The processing (always digital ;-) is huge and needs to be really fast to enable real-time playing. The only such instruments I know of are keyboard (MIDI) based.. IF one was to build such an engine which was directly controllable from the theremin interface (without the latency and data transfer bottlenecks of MIDI) one could achieve what you are after.

Other synthesis methods could also hypothetically be used - these include additive synthesis, granular synthesis and FM to name a few - The key thing IMO is getting ALL the player data into the engine at full resolution with fast transfer.. If one can do this, one can synthesize the sound using whatever engine you want.. But such an interface and such instruments do not yet exist AFAIK.

It could be done - A much better replication of a violin could be achieved - but it would require dedicated R+D - it could not be easily cobbled together with existing technology.

Fred.

"Here is a spectrum of a violin:"

Its a nice spectrum of one violin played at one given pitch in one way - its not a "spectrum of a violin" its a tiny snapshot... That sound put into a percussive envelope shaper wont sound like a violin, shifed to some other frequency probably wont sound much like a violin, and played from a theremin without being modified as pitch and dynamics change probably wont sound much like a violin.

If you have ever played with a sampler you will understand this - to get a reasonable emulation of any acoustic instrument you must make numerous samples of that instrument played at different pitches and amplitudes - take one sample and replicate that waveform (spectrum) over more than an octave (sometimes less) and it will sound really fake everywhere except at or close to the pitch you recorded.

The human voice is the most easy example - it is an acoustic instrument with exciter and resonator.. Record the voice at one octave, play it back an octave lower or higher, and you notice that its not a "normal" voice! ;-)

Yes - with a basic triangle wave and some tracking filters you can get a reasonable approximation - but like formants in the human voice, violins have some fixed resonances - these are where the "crafting" of sound comes into play - the better the crafting of the resonances and waveform feeding the resonator, the better the results.

You probably would need to have a few fixed band pass filters, a ramp waveform, and at least one low pass voltage controlled filter to get close to emulating a passable violin - the spectrum would change as the frequency changed because the fixed bandpass filters wouldnt be moving with the frequency.

This:

Is just a quick guess as to some influences that may be involved with your violin spectrum - real crude.. but if you saw the purple curve as the harmonic energy levels from the exciter / bridge (or ramp waveform / Low pass VCF) and the yellow curves as a few of the fixed resonances in the violins construction (bandpass filter gain) then the resulting waveform (spectrum) is produced.. This is extremely simplistic, because the ramp waveform will be changing (rising and falling slopes changing angle) and other resonances will appear / change / disappear in frequency dependent ways.

Alex,

I have pasted a schematic in a post above..

I may not be about much over the next few days - Got some pre-court hearings about my divorce and access to my children, and depending on how those go may or may not feel like talking to or helping anyone. It may not be as bad as I suspect, and will probably be postponed yet again on some technicality -

But if I disapear, its not because of you! ;-)

If I dont get back before your presentation, I wish you all the best with it!

School is important - but the biggest mistakes one can make in life are are nothing to do with the head stuff - the important lesson to learn early is BEWARE OF WOMEN!

;-)

Fred.

OT: I wouldn't say "Beware of women" in general, Fred. I'd be more specific and say "Beware of Ferengi, Romulan, and Klingon women, only trust Betazoids!" but the latter are unfortunately very rare...

Hello,

well, I hope the very best for you, Fred. What Ive learned so far about woman is actually... nothing. I try to be myself, and the right ones stay and the wrong ones go.. But okay, I am just 18 years old, probably there is a lot to come. I am sure it will turn out well for you. ^^

But, about the circuit you've made. I feel uncomfortable, because there seems to be lot of work behind it, but I am afraid that it wont work out for me (I miss several parts and it will cost too much time regarding the risk of not working because of tuning issues etc.).. I must minimize the whole thing. I just want to build a single oscillator - without any antenna and a reference oscillator. Just one simple Armstrong- oscillator that produces some sound. I am afraid that I dont have more time than that because I should slowly finish the whole presentation... There are only 2 Days to go...

Could you / or anybody else help me with that simpler goal?

Sincerely,

Alex