"if the theremin became easy to play with a redesign of a few aspects?" - Christopher
My inclination has always been that linearity is the key to easier theremin playing, particularly for beginners..
But I have not found "technically correct" linearity (as in, note intervals as equally spaced as possible) helped me a lot.
I found that different theremins have, for me, some charactaristic which either makes them playable or difficult / unplayable - and this 'quality' is not directly related to "good linearity" - but I do think it is related to the 'curve' of the playing field.
The instrument (apart from my own prototypes) which I found by far the easiest to play was the Tvox Tour.. I do not know the field profile on this, but I am told it is far from linear - To me, it is beautifull, and feels "linear" - or, what I should say is that to me the note intervals feel instinctive.
My 2nd favorite is probably the E-Pro .. I know this reportedly has good linearity. Then there is the EW (and I have "played" several, some feel better than others, but, to me, all are extremely difficult) - I have no idea why I have difficulty with the EW, it has a reasonably good linearity when well tuned.. But I find it as hard to play as some theremins which do not have equalization at all, and are really non-linear (SC EPE and the Australian variant - I forget its name)
The above observations cause me a problem - I do not know exactly what it is that makes a particular theremin easier for me than any other theremin, let alone whether this is "universal" or whether each individual would have an optimum curve best suited to them.
My H1 theremins highlighted this - I had 4 different EQ schemes employed on these, with the aim of seeing which of these theremins people found easiest to play - Alas, the nature of the event made accurate recording of and derivation of useful data nearly impossible, but the 4 theremins fitted with severely modified front-end (lower operating frequency, larger tank capacitance, larger EQ inductor) giving the most linear response, did SEEM to be the most popular.
This 'result' was probably biased because I found these to be the most playable of the 16, so I tended to use these most, and tended to give people "lessons" on these most... But, in general, people who managed (without my help, often after having visited the show repeatedly and played the theremins - usually at lunch break time or early evening when there were crowds wanting to play the theremins) to play a tune, did so even on the most non-linear instruments.
Fred.