Yeah, I thought you might be into this. I think it has a really rich tone. What a different musical landscape it might have been had this been built, though given the complexity, I wonder if tuning was one potential reason why it was never built. It could just be that manufacturing at the time wasn't up to it. It also says that it shares some similarities with the harpsichord, so I wonder if that means that it can't change dynamic? Anyway, here is another video of it which seems to explain more about it . . . if you speak Polish. There is some more music included though, as well as a better view of it being played.
Given the description, this thing sounds like a beast to manufacture- four spinning horsehair wheels? And each key presses the entire string down onto the wheel? And upkeep would be... rigorous. Horsehair frays, and the microhairs (technical term? Dunno) that create the tone wear down. And new hair stretches I think, which means that every time you replaced the hair on the wheels, you'd have to spend time "tuning" just the bow part of it so that it wasn't too loose. To say nothing of the steel strings. Re. dynamic- sounds like dynamics were taken into consideration. Harder the string presses onto the wheel, and the faster you pump the foot pedal, the stronger the tone you'd get. Like a violin. And an organ. Maybe a little less dynamism. The harpsichord has no dynamic variance because every string is plucked by a little fork on hitting the key, and the fork jumps at a fixed rate regardless of how hard you hit the key. THE MORE YOU KNOW
I wonder if the spinning "bow" has to be adjusted or replaced often?