When I practice with my EPlus, some days I am more perfectionistic with the tuning than others.
I have found that if I carefully apply Thierry's indications of tuning the middle register with the pitch knob and the lower register with my body, I can get five almost linear octaves as he says. I don't know if the EPro gets much more linear than this, as I haven't tried one, but I'm very satisfied with the linearity of the EPlus when tuned in this way, the differences between octaves are very small.
On the other hand, there are days when I don't tune so carefully, maybe because I don't have much time for the theremin and I want to squeeze it out as much as possible, or maybe because it has been a hard day at work and I just feel like playing relaxed and without worrying too much about improving.
The thing is that, when I record myself playing and hear what I have done with a more perfectionistic vs. a more sloppy tuning, I don't notice much of a difference. It seems that if I care less about tuning and have a less linear field, I just end up adapting my hand gestures so the final result is similar; and this has the extra advantage that if the field changes a bit over time it's not a big deal. However, I'm aware that this may be because I'm not good enough for careful tuning to make a big difference. Perhaps for my current level of playing it isn't important to tune very precisely and carefully, but when I keep improving I will hit a roadblock if I don't do it.
So I would like to have the opinions of more experienced players: do you think it is important to tune very meticulously, or that it is OK to be more lenient and do a more coarse-grained tuning, trusting oneself to adapt to slight changes in the field?