noobee today

Hi all Theremin fans, this is my first time on the forum, so I thought I would intro myself.

Being now a retired organ/keyboards technician, having too much spare time, and missing conversing in things electro-Thereminny, it was decided to look into what's happening here.

The last time I played around with the subject, I had completed an experimental instrument, that was strictly semiconductor (transistors) based. In brief, it contained 1 master oscillator plus 12  more oscillators identical to the master. Then 12 mixers each followed by independent level controls, plus some rough filters for tonal  manipulation. The end result produced some seriously strange, and yet, beautiful sounds. 

The master oscillator was constructed in such a way so that: frequency drift due to temperature was kept as low as was physically possible, the whole master oscillator being held in a metal container, and pumped full of stryro-foam type insulating material. 

I remember how sensitive I was able to make the main 'antenna':  setting the frequency of one of the 12 outputs to about 10 Hz (cycles), I noted a shift (growl) in frequency of about 5 Hz when I waved my arm whilst standing about 2 Metres away from the 'antenna'. (The volume pad being overidden for the experiment). Weird that: walking around the perimeter of the room, noting the thing change in response.

Having often thought about the fun I had during those times, I have decided to revisit the scene of the crime, and rebuild another.

Thanks for the patience fellow Thereministers.

Hello Peeth,

Facinating experiment! - I presume you were trying to get 12 semitones from your 12 (prsesmably fixed frequency) oscillators, all heterodyning against one variable oscillator.. ? (!) - Or were these intended to form an additive harmonic engine? 

"The end result produced some seriously strange, and yet, beautiful sounds." - I have no doubt that it would! ;-) .. Whether going for semitones or harmonics, such an "engine" will not track consistantly - There will only be one (at best) frequency from the master (variable) oscillator at which the tuning of the other oscillators will provide a musical relationship.. (if you are interested, email me, or say so here - I dont want to go to the effort of explaining and producing another long-winded posting if no-one is interested ;-)

But multiple heterodyned oscillators is certainly a facinating field to explore, and even when not "musical" does produce sounds which are interesting and often "beautiful" when used in the "right" context - Quite similar at times to what one gets from ring modulators driven from complex waveforms.

Welcome to TW.

Fred.

Hi there Fred, thanks for the welcome, its nice to hear from you.

I played many games, and many happy hours were spent with Theremin related things . My first efforts in hetrodyning began when I constructed an audio signal generator for testing purposes. The generator was a BFO type, and as you will no doubt understand, not too far removed from Theremin's basic instrument. After building simple Theramins, and not being the type to leave well alone, I chose 12 fixed oscillators, each centred on approx 455 kHz, but each able to be shifted from the centre frequency by a few percent. The reason for 12 as a number is because my background was in organs and keyboards, and I kind of had a notion of semitones, but in I really just wanted to hear the effects of multi frequencies (Thereminic polyphony?). This meant that when the master was shifted in frequency (via waving the 'antenna'), the result was, in effect, a gliding 'dischord'. Many harmonics were generated and passed on to the resultant audio. The master osc was buffered, amplified and then fed at low impedance to each of the 12 secondary oscillators. Each of these being then mixed by a single diode, and then some basic audio filtering was applied to each output, and finally fed to a 12 input op amp summer, this gave some control over each level before final amplification.

I tried also the other way: varying the frequencies 12 oscillators, mixing the resultant frequencies with the output from a single crystal oscillator. I had a system of 12 'antennas' in a line, and had lots of fun as a result. 

One time I built two identical Theremin circuits, and the combined output level (volume) was controlled by a simple foot pedal. One 'antenna' was on the left side and the other on the right. Between both 'antennas' I fitted a long brass strip set below a series of brass round headed tacks, these were part of an arpeggiator system I had included. I used a total of 36 individual 'sawtooth' oscillators, each gated to make various bell-like sounds, switched via the panel brass fittings explained above. 

I think I left off playing with Theremins when I attempted (without success) to construct a kind of stringless 'Steel guitar'. 

You said:

"such an "engine" will not track consistantly - There will only be one (at best) frequency from the master (variable) oscillator at which the tuning of the other oscillators will provide a musical relationship."

Yes of course you are right Fred, and the maths proves the point. Just two sines mixed together (multiplied) in a non-linear device such as a diode) will provide the sum and difference frequencies, plus the two original frequencies, (and an infinite number of related harmonics) so 13 oscillators would be a nightmare to calculate, but the aim was never to achieve a musical instrument in the common sense, rather to (hopefully) generate new  sounds. Where the usual case is to remove the so-called 'unwanted' harmonics, I found them useful when playing with sound 'textures'. Then there is the problem of frequency drift.

I laughed when you mentioned Ring modulators, boy what games I played down that alley! Harmonics flying all over the place. 

Great fun.

" but the aim was never to achieve a musical instrument in the common sense, rather to (hopefully) generate new  sounds." - Peethagorus

Ok, I was hoping this was the case.. Thats why I didnt go deeply into the science of the matter - If you had been trying to produce semitone or harmonic series intervals and not been able to, I could have shown you why - But you know why, so I dont need to do that! ;-)

My focus has been primarily on "conventional" musical relationships - I love additive synthesis, as this has the potential to recreate the sound from any musical instrument (as well as creating sounds for "impossible" instruments) and have developed a heterodyning additive engine using mixed signal techniques (PLL multipliers locking LC oscillators).. With such a system, by programming the PLL deviders, one can generate harmonic series and / or semitone relationships, so can either do additive synthesis or produce thirds, fifths or whatever - combining the voicing as one wants by assigning the PLLs (as in, with 12 "voices" one can have 3 seperate "voices, each with control over 4 harmonics - or you can have one voice with control over 12 harmonics - and you can select which harmonics you want to control - so if one only wants odd harmonics, you can effectively resolve a waveform to 24 harmonics)

The trouble though with all this stuff is complexity - To do what I want, one needs to adjust the level of each harmonic dynamically as a function of frequency and volume - Doing this, all one needs is a spectrograph of the instrument you want to "duplicate" and you can do so, perfectly.. But if one tries to give the player a user-interface to facilitate adjustment, one either ends up with a multi-menu digital interface which, even with simplification, is horrendous - Or one ends up with enough knobs to make a full Moog  Modular look like a toy Gakken synth by comparison -- Or one sets up a few dozen presets... The cost of such a beast would be high, and the market just isnt there.. So I have gone back to the simplicity I find in Lev's designs.. I want to make a Clara-min.. I could achieve this with additive, but I am hoping to get close enough using simpler technology.

.... But I still am drawn to the idea of a multi-source additive with its unlimited possibilities..

However.. I am also into weird sounds, so your kind of experiments are facinating! - The best "synthesiser" (as in, the one I had most fun with) I ever made was when I was 14 - Poly synths did not exist, so I made one using VCO's driving top-octave generator IC's (back then one could buy these - Although I had to import them to S.A. from the U.K.. I Think from Maplin.. ;-) ... I knew nothing about aliasing or how strongly the edges of square waves propogated across thick bunches of cables, LOL - And every note I played fired up some adjacent tone or envelope generator, the signals found their way over the supply rails, and the result was a mess - But there were people (even back then in 1970) who thought it was amazing, so I was able to sell it for a tidy profit, and start a real (musical) poly-synth which was well behaved but comparatively boring!

Fred.

"The best "synthesiser" (as in, the one I had most fun with) I ever made was when I was 14 - Poly synths did not exist, so I made one using VCO's driving top-octave generator IC's (back then one could buy these - Although I had to import them to S.A. from the U.K.. I Think from Maplin.. ;-)"  - FredM

You can do top octave generation in an FPGA super easy.  I have a verilog construct that I like to use which gives arbitrarily close precision and fairly square waves.  Like DDS, if you add phase to an accumulator you have an NCO.  Unlike DDS, the accumulator isn't necessarily a fixed power of 2 wide and is adjustable.  The phase adder is a multiplier, the accumulator is a divider, so it's just a matter of adjusting this ratio to get the frequency you want (and perhaps follow this by a divide by 2n stage to keep the accumulator from being too wide).  It can use a much lower input frequencies than traditional division only methods, but lower input frequencies unfortunately give higher jitter.

Hi Dewster,

Actually, what you said (about FPGA's) just reminded me - I remember now that my first synth didnt use top octave chips.. my first used as stack of 24 74-series (74193s I think) to devide the VCO/s (8 bit divider using two 74193's).. LOL ;-) The crudeness of the resulting frequencies added to the instruments "charm".. It was my 2nd poly synth which used TOS chips.

While on this whole organ related topic - some (most/all TOS chips can be difficult to get these days.. I have programmed PSoCs to replace their function for someone who was restoring an old organ... These parts are ideal, having just enough 16 bit deviders available if you use all the digital blocks and route the internal clock deviders to output pins.. at about £6 a lot cheaper and easier than finding some rare TOS.

"Like DDS, if you add phase to an accumulator you have an NCO.  Unlike DDS, the accumulator isn't necessarily a fixed power of 2 wide and is adjustable.  The phase adder is a multiplier, the accumulator is a divider, so it's just a matter of adjusting this ratio to get the frequency you want (and perhaps follow this by a divide by 2n stage to keep the accumulator from being too wide). "

I have started playing with Quartus II and exploring the Altera FPGA stuff - The chip on that low cost board ($20 , £13) has two DPLL's as far as I can see, so I am really interested in the possibilities... First job is to multiply reference and VFO's, to produce a multiplied difference frequency (perhaps 160Hz from an audio difference of 16Hz) and use this to generate the timing signals to drive a period voltage for conversion to a 1V/octave output without latency and which can track the full audio spectrum from 16Hz up...

It may even be possible to eliminate the analogue here and simply count the period..... ? not done the sums, and im not even sure what maximum clock is, so its right at the start - I have done the above (in analogue) using my PSoC 3 development board, but the PSoC boards are expensive compared to the FPGA boards (about £35 compared to £13)..

IF I could take the reference and VFO from a theremin front end, slap these into an FPGA board, output to a 12 bit DAC, DAC outputs 1V/Octave.. And the FPGA also outputs waveforms (Triangle, Ramp and Square) from mixed signal heterodyning (after simple RC filtering):

with register switching included, this could be quite a nice little add-on for any thereminist who is also into synthesis.

(the only really tricky bit is the exponentiation of the period value or volts/Hz to convert this to volts/octave - probably not tricky, but for me, doing this in something like a FPGA is gouing to be CHALLENGING! LOL ;)

Fred.

Oh, BTW - If I had known that Quartus had block and schematic entry mode, I would have got into it far sooner! - Every thing I had read seemed to be Verilog based and script centred.. Then I found this little tutorial showing logic gates and hierarchical blocks being drawn.. Played with it, and its GREAT! ... I can do things the way which is natural to me - draw a top level with sub level blocks, and fill these blocks with circuits or verilog or whatever I choose..

"The chip on that low cost board ($20 , £13) has two DPLL's as far as I can see, so I am really interested in the possibilities... First job is to multiply reference and VFO's, to produce a multiplied difference frequency (perhaps 160Hz from an audio difference of 16Hz)"  - FredM

Unfortunately the PLLs are more for high speed digital clock management (multiply up a crystal, trade fabric speed for improved I/O timing, etc.).  They only work down to 10 MHz or so.

"Oh, BTW - If I had known that Quartus had block and schematic entry mode, I would have got into it far sooner!"

Didn't know that was still in there.  For me blocks & schematics tend to decrease readability, make verification more difficult, and kill portability.  Real men code in verilog! ;-)

"(the only really tricky bit is the exponentiation of the period value or volts/Hz to convert this to volts/octave - probably not tricky, but for me, doing this in something like a FPGA is gouing to be CHALLENGING! LOL ;)"

My LED "tuner" does that, it's log_2.v that uses squaring and shifting.  I/O width is parameterized so just set it to whatever you need.

"Real men code in verilog! ;-)" - Dewster

LOL ;-) - I knew I was asking for some comment like that!

Some years ago when talking about "real" coding of mathematics, I got a similar chauvenistic comment from Thierry... Yeah - What insults are we going to use when 30% of engineers are women ? ;-)  .. Yeah, I know, thats not going to happen.. and even if it did, we wouldnt change! LOL ;-)

The "trouble" is that I am not easily able to 'multiplex' my brain across different "diciplines".. When I am thinking about circuits, I am thinking about circuits - not code.. And when I am writing code, I am primarily thinking about sequential operations .. Yes, I know that writing code, even for a MCU, one does (or can) effectively do "circuit" operations like orring and shifting etc, and I am fine with this - But when it comes to defining the operation of even a simple schematic like the one shown above, I find it MUCH easier to just draw the schematic than to code its functions, and much easier to visualize its operation than I can from reading as script... The more complex the circuit, the worse this "gulf" becomes for me - I can look at a A3 page of NEATLY drawn schematic and see almost instantly what it does and how it works (one recognises configurations instantly, and puts the whole thing together subconsciously in seconds) but even half a page of A4 VHDL or Verilog takes me a long time to decode, let alone write.

So I am happy that Quartus still has this functionality, and happy that I found it! - I will be sure to copy the program to CD just in case the "real men" win and they remove this feature in some future revision!

;-)

"Unfortunately the PLLs are more for high speed digital clock management (multiply up a crystal, trade fabric speed for improved I/O timing, etc.).  They only work down to 10 MHz or so."

- Not a real problem - it is easy enough to create a couple of powerful phase/frequency comparator using (schematic ;-) logic, and implement  simple VCO's.. a simple RC filter on each and I have  PLLs perfectly capable of locking and tracking the tiny frequency variation found from the VFO even in the most extreme cases (<< 5%) .. My FPGA will be grossly under-used anyway.

"My LED "tuner" does that, it's log_2.v that uses squaring and shifting.  I/O width is parameterized so just set it to whatever you need."

Thanks for that clue.. If I can get away from using the transistor transfer function (which involves using a transistor array in an oven configuration) for exponentiation, and not lose too much resolution (as in, voltage steps correspond to 1 cent or less ideally) things become simpler - Oh, theres no real problem with transistor exponential converters if one controls the temperature - but I need the FPGA to simplify the timing pulses anyway, so if it can do the whole job, why not... Except that I then need a DAC )-: .. It may actually be cheaper to stay with the analogue approach..

Thanks for your help, Dewster!

Fred.

ps - I believe that schematics can be compiled to Verilog or VHDL.. I know I can do this with my Vantis software (I have used the Vantis software to generate VHDL from schematics for past projects where the client wanted VHDL for their CPLD's - I generated schematics and "machine generated" code, and passed these to a engineer who tidied it all up..  But that was a really long time ago..)

Hi again Fred, and hello there Dewster (like your graphs!)

Fred, you said "I love additive synthesis" and your experiments obviously bear that out. It takes a great deal 

of time and patience to create an "heterodyning additive engine using mixed signal techniques (PLL multipliers locking LC oscillators)", and it takes much skill to program and interface or 'play' such a system. Just the notion of phase-locked generators would be beyond most enthusiasts. Your comment re "a full Moog  Modular" made me smile: In the early seventies I was approached by Radio City in Liverpool, as they were trying to help two visiting musicians. Their Moog system was in need of repair, it turned out that the musicians in question called themselves 'Tonto's Expanding Head Band'.

Of course that Moog system is a subtractive synthesizer, but it certainly managed to produce some good stuff.

(I don't think Moog made an additive synth, but I may be wrong).

You said "To do what I want, one needs to adjust the level of each harmonic dynamically as a function of frequency and volume - Doing this, all one needs is a spectrograph of the instrument you want to "duplicate" and you can do so, perfectly.. But if one tries to give the player a user-interface to facilitate adjustment, one either ends up with a multi-menu digital interface which, even with simplification, is horrendous -""

And I agree such a system would certainly be a great challenge, but you almost give your solution in the same paragraph: It seems to me that such a system lends itself to software, perhaps based on Csound, where one might construct almost anything which would perhaps be to difficult via hardware methods. With the right software, and a great deal of time, you might achieve what might seem to complex in terms of resistors, capacitors and a whole bucket of exotic semiconductors.

You said "The best "synthesiser" (as in, the one I had most fun with) I ever made was when I was 14 - Poly synths did not exist, so I made one using VCO's driving top-octave generator IC's " and this made me chuckle, as I too went down a similar path - at least in the sense of those top-octave chips: I used to own a 'keyboards' repair company in Scotland, and one day this guy turned up at the unit with a huge and an ancient Lowrey organ. He had it on a trailer, and had pulled it up the M6 all the way from Middlesex. He took it to Scotland every year because he paid for his holiday by playing, but it stopped producing notes, and he took it to a firm in Edinburgh. The firm told him it was beyond repair, but unknown to the owner, they had taken out the top octave generator chip. He asked me to get it working again, and we agreed on a price of about £120. According to the service manual, it had a first generation type of top-octave chip. The outputs drove a series of dividers, the dividers too were first generation cmos chips, and the modern replacement generators required a shift in logic levels. An apprentice of mine had by that time become the service manager at Yamaha (Kemble Organ Works, Milton Keynes) and he posted me a pair of 6 note top octave chips, (which I paid for) these being used in certain Yamaha organs at the time, and seemed the easiest option (electrically speaking) as replacements. Meanwhile I set about stripping out the old circuitry, and converting the Lowrey to take the new chips. The new chips duly arrived, and I spent that evening playing and testing the organ.

When the owner arrived to hear his darling organ he was full of praise. But he somehow forgot the price we had agreed upon (handshake), and his tone (not the organ) changed. As I was well out of pocket, and realised this guy wanted to pay about £20, I removed my conversion circuit board including the new chips, and gave him his organ back. I doubt if he ever got it going again.

You said "I knew nothing about aliasing or how strongly the edges of square waves propogated across thick bunches of cables," and I agree wholeheatedly with that. I am perhaps from an earlier generation than yourself, so my early experiments did not include top octave chips, instead my generators were 12 valve (tube) Colpits oscillators, each 'coil' being the size of a small mains transformer, and the laminations, (E I shapes) were arranged such that the E plus copper windings remained bolted to the chassis, but the I laminations (held as one bar) were spring-loaded, and the end result was that the air gap was adjusted, thus the inductance changed, and therefore the frequency. Crosstalk? oh yes indeed, with signals sitting on dc levels of 250 volts, horrendus is an apt description. The whole thing weighed a ton.

You said "But there were people (even back then in 1970) who thought it was amazing" and I am not surprised, the construction of such a complex instrument as you describe, would have seemed to the average Joe like you delved in some kind occult art. I have always found it interesting to investigate what the average person perceives when confronted by such 'complicated' things. But that's another subject.

You are obviously into additive systems Fred, but I wonder what your opinion is concerning FM (aka Yamaha) synthesis?

In passing, I do apologise to any forum member who finds the context of my posts too technically difficult to grasp. Please post if this is the case, and I will cut back on the jargon or give an explanation.

regards

"In passing, I do apologise to any forum member who finds the context of my posts too technically difficult to grasp. Please post if this is the case, and I will cut back on the jargon or give an explanation." - Peethagorus

LOL :-) .. I wouldnt worry too much about that! ;-)   .. I think that most people here know that any thread I get involved with "degenerates" into incomprehensible techno-babble ;-) - I even introduced a rating system for my posts, which I will use here:

Technical mumbo-jumbo warning:

NERD RATING 32.0 - likely to be comprehensible to most educated technical people, but of doubtful interest to those who are not nerds.

 (Max value = 42) . 0 to 5 = likely to be comprehensible to most people. 5 to 10 = likely to be comprehensible to most educated people. 10 to 20 = likely to be comprehensible to most educated technical people. 20 to 35 = likely to be comprehensible to most educated technical people, but of doubtful interest to those who are not nerds. 35 to 42 = Truly of interest only to nerds - may be in the domain of metaphysics!

"It takes a great deal of time and patience to create an "heterodyning additive engine using mixed signal techniques (PLL multipliers locking LC oscillators)", and it takes much skill to program and interface or 'play' such a system. Just the notion of phase-locked generators would be beyond most enthusiasts."

Analogue additive synthesis is almost impossible if one works with audio frequencies - one of those lovely ideas which are just too complex to implement - the reason for this is that tracking the wide frequency span (16Hz to say 5kHz, or even reducing this down to 5 octaves) is far too wide for standard frequency tracking circuits, and also, as the frequency drops below 100Hz, the latency increases (time required for even one audio cycle) makes the system impractical (Pitch to voltage converters for example do not behave below about 100Hz - As anyone who has tried on an EW+ or E-Pro will have found)..

But one overcomes this problem completely when using heterodyning tone generation - One is not dealing with audio frequencies, one is tracking HF oscillators with only a tiny variation in frequency - instead of having to track 5+ octave (>32:1) one only needs to track frequency variations equivalent to a couple of semitones if one was to scale this down to audio.. It is the ideal topology, and makes analogue additive synthesis possible.

Whilst I have been interested in analogue additive since the 70's, it is only in the last 5 years that I have actually built an additive engine which REALLY works - and this was entirely due to revelations I obtained from working with theremins - A simple additive engine can be EASILY constructed using mixed signal techniques employing heterodyning two high frequency (digitally multiplied / devided ) sets of frequencies - Using PSoC 3, this can all be done in one chip.. That was my proof-of-concept... A few minor difficulties regarding updating the data without glitching when changing the amplitudes / phases as a function of frequency/volume, and the PSoC is not the ideal part - I am now looking at FPGA with external analogue sine oscillators (VCO's) locked to PLL's implemented in the FPGA, and doing analogue heterodyning on these.. `16 stages (32 PLLs/VCOs) with a VCA on one set of oscillators (16) summing into one mixer, would give absolute control of 16 harmonics.

" I wonder what your opinion is concerning FM (aka Yamaha) synthesis?"

I messed about extensively with analogue FM (as most people back in the early days probably did) for creating weird and atonal sounds, bells, that sort of thing (noise into a VCF, VCF output modulating VCO frequency, to create complex wind type sounds a bit like Elton Johns "funeral for a friend"... But FM using configurable "operators" where one could actually model an instrument was well out of our reach until digital synthesis appeared.. I think the closest analogue ever came to this was with phase / pulse-width modulation.. but again, there was just too much complexity and too many modules were required even for the simplest task.

When the DX7 appeared, it was revolutionary - I was one of the people who jumped on it - never managed to afford a DX7, but bought a cheaper Yamaha FM synth, then bought a Yamaha MSX computer and FM card for this, and started into the world of FM... It didnt take long before I became bored / dissapointed with this technology - IMO, it took all the fun out of creating sounds - no knobs to twiddle, nothing at all intuitive or instinctive (to me) in the algorythms... As an engineer I was busy all day doing engineering - the last thing I wanted from my hobby was to be continuing essentially the same stuff (and the most boring aspects at that) in my leasure time. I actually grew to dislike FM so much I got rid of my FM kit and got into Rolands D50 archetecture (with a D110) which IMO sounded much less clinical, The best of that digital era was, IMO, the casio CZ series which was FM really (phase modulation) - but it was much easier to hack the guts of a CZ101 to get it to sound interesting.

Oh, I love subtractive synthesis - It produces wonderful sounds which were "new" and exciting - But it is extremely limited in terms of sculpting complex waveforms as one gets from acoustic instruments or electronic instruments like the theremin.. Additive IMO is the best technology by which to do "emulation", and also offers unlimited possibility in terms of creating "new" instruments. The other technology which I have never really got deep into, but really interests me, is Physical modeling - For acoustic this looks like the way forward, as if your models are accurate, you should be able to create / emulate any physical acoustic instrument and be constrained by "real" physical parameters.. Or you could change the "laws" and create instruments which could only be realised in another universe... (?)

It seems to me that such a system lends itself to software, perhaps based on Csound, where one might construct almost anything which would perhaps be to difficult via hardware methods.

Yes.. :-( .. I really do prefer "physical" instruments.. To me, the moment one needs to get into a computer, mess with parameters, click on menus, all that stuff, the fun goes out of it and the creativity seems to evaporate... I think this is because of my lack of musical competence - When I am "moved" to create something, I need to just sit at then keyboard or whatever and play / twiddle knobs ... Even starting the software recording process can be enough to make me lose my "moment" - So I have (well had - all in bits right now) a setup where I had the midi and audio recorders running, and keyboards all ready to roll - Turn on, start "playing", twiddle knobs in real time, and capture hours of rubbish.. But I always knew where, amongst the "rubbish", I could find what I deemed to be "gems" - and occasionally I could extend these "gems" into a full piece.... If at any time during that process I was to go into the "technical" aspects, the session ground to a sticky end.

My focus has been on theremins - Additive is a means to an end, the end being to produce the sounds people want from their theremin.. I know it IS possble to "copy" any sound based on a standard harmonic series (as in, a sound with no atonal components) and reproduce this, complete with all pitch / volume functional variations, if one has a fully implemented additive engine - and IMO this is ONLY true for additive, one cannot make this statement for any other synthesis method (I do not regard sampling / wavetable as synthesis - but do not believe that even sampling technology could fully capture the operation of a theremin).....

But entering the required data is where things become difficult.. Perhaps with an editing package on PC and a SD card it would be possible to provide patches for RCA, Claramin and other popular theremins, and add to these over time.... Perhaps even something simple like a text string defining harmonic levels at each semitone, which could be put together in a spreadsheet with data extracted from sound samples..

From what you say, I assume you are in the U.K.. (?) Perhaps we could get together some time .

 Fred.