Hi there
I've designed the Chimaera above, Fred was so kind to invite me over here.
I dont really see a way 'round this.. other than an audio preview (which I am adopting for my ribbon) - As soon as one has tactile 'markers' one interrupts the movement 'flow' - when whizzing over a smooth slippery surface one can get the "flying" - any indentations or whatever will, I think, give a "trigger" as they are moved over - If they dont give a trigger signal, then IMO the surface probably isnt sensitive enough..
@Fred, this pretty much matches my initial design goals, I just went one step further and made my device touch-less from the beginning, just like the theremin.
I wanted to have some kind of polyphonic ribbon controller. Initially I've experimented with capacitive touch sensing, ultrasonic and IR proximity sensing and IR touch table technology, but it just did not feel right. Altough some haptic feedback is nice to tell your brain that your fingers have hit a surface, I've made the experience that it's not essential. In the contrary, when touch and pressure is involved, mechanical resistance and friction tend to slow down and lower expressiveness of my play (and expressiveness is what continuous controllers are all about).
What I ended up pretty much is a continuum fingerboard with just one row of hall-effect sensors and stripped off all its mechanical parts. The magnets instead are directly sticked on fingers and "flown" over the sensor array.
Im sure you could play a mono fingerboard or ribbon with your eyes closed - I doubt you could for a poly, even if there was tactile marking
Polyphonic play over a continuous surface is surely is hard, but you do not have to rely entirely on your ears only, a great part can be offloaded to muscle memory (needs its practice, though). I'm slowly mastering diphonic play and have a long-term goal of reaching quadrophonic play, eventually. Higher polyphony with my touch-less design is not practical, IMHO.
I suppose if one could have an overlay to place on a smooth fingerboard, which was engraved or whatever to give tactile feedback, you could get the best of both worlds...
For long jumps on a continuous surface I prefer visual cues and muscle memory, the fine adjustements then are done by hearing. It may be hard to capture all engravings during a fast transition.