I have no information yet on Mr Engels. Doing researh on the web on how the fingerboard might work I found a product made by Doepfer . It is call the R2M -> Ribbon to Midi controller. They used an industrial “Position Sensor” for the controller. Check the web site for more details http://www.doepfer.de , it is very interesting. You can download the user guide for the product for more insight information.
I just put all my web-site research addresses into one archivo, but its late and i haven’t been able to put them into the forum context- drrrr– So if u wish, send me your real authentic e-mail address and i will send this wealth of info to u
John Spindler firstname.lastname@example.org
I´ve seen the Doepfer products, they are interesting. When I get the time Ill send you all the internet addresses Ive found (there are many) dealing with ribbon controllers, linear potentiometers, conductive plastics etc. I have had some success in my kitchen myself, creating quite a few linear potentiometers using various strange mixtures of epoxy, paint, graphite powder, carbon powder etc.