Rupert - I'd love to hear that. Is there a clip on the web?
Kevin - terminology is a problem. Precise meanings of technical terms seem to vary from website to website, depending on what particular area of electronics or music is being covered.
Lets see if I can explain myself a different way.
I am interested in modifying the sound of my instrument to increase it's versatility, but in a non-destructive way. That means not clipping the waveform to approximate a square-wave, like the majority of guitar distortion boxes, or rectifying it like an octave-up box and so on. I have no objection to delay based effects - love my little echo-box, but am looking for something different...
The simplest electronic instrument would be a circuit that generates a sine wave in the audible range, with a potentiometer attached to vary the frequency. That's the basis of a tannerin - a Voltage Controlled Oscillator and a slider to vary the control voltage. Adding partials to increase the complexity of the sound would be a simple matter of feeding the control voltage to a bank of VCOs, varying the voltage that each one receives by a fixed amount by adding different resistors into each feed. By choosing the fixed resistances so that each one was an exact multiple of the lowest frequency, and by providing a means to vary the amplitude of each of the resultant sine waves independently before combining them one could create a synthesiser capable of producing a variety of waveforms, some of which would be reminiscent of other musical instruments. Essentially one could control the timbre of the instrument in terms of which harmonic partials are present and in what proportions. With a bank of sliders to control the various amplitudes the positions of the sliders would correspond directly to a spectrum plot of the resultant sound. You could effectively draw the spectrum you wanted to hear.
And, as an extension, the ability to change their relative pitches as well, to provide for non-harmonic partials. (I get that using a ring modulator gives non-harmonic partials but somewhat chaotically for my purposes.)
Kind of a bank of tannerins, all squooshed into one box, and sharing whatever bits of circuitry don't need to be separate. Let's call it a Synthesising Tannerin.
So instead of your tannerin showing a single spike on it's spectrum, you might have half a dozen spikes - depending on how many VCOs are involved. (I gather that high order harmonics are generally undesirable - or inaudible - so I guess that is a sensible number.)
Of course theremins don't make a sine-wave. I'm not sure what the name of the wave it makes is, it looks kind of sine-wavey on the oscilloscope but a spectrum plot shows a neat little rhombus instead of a single spike. That's the characteristic sound of my Kees, and I don't want to lose it.
I've got this funky little piece of software that shows real time spectrum plots, and it's pretty cool watching the rhombus slide up and down as you gliss. It's also neat watching it at work with an echo box attached - loads of little rhombi all sliding up and down and through each other. And - as I mentioned ages ago when I noticed it, while my Kees was warming up it was producing two rhombi all by itself, and glissing caused them to move in what looked like a simple mathematical relationship. And the sound it made was not unpleasant, just a tadge warmer than usual, but still recognisably a theremin. So not necessarily a bad thing. But I would like control over it, as per the Synthesising Tannerin described above, but instead of half a dozen spikes in a predetermined and fixed relationship to one another, half a dozen rhombi.
Does that make sense?
(Oh, and would it be an expensive way to go about it? I paid about 185 dollars for my Kees which is based on a $54 Jaycar kit - it wouldn't need a bigger box, there is plenty of space in the enclosure, nor would it require any
