How fascinating, Mat! I've never seen anything like that before, but according to the YT comments it's a Japanese "Chromatone" keyboard which allows you to use the same fingering, regardless of key. Sounds like a bright idea to me, but it will certainly have an uphill struggle knocking the conventional keyboard off its perch! Unfortunately the wrong notes aren't a very good advertisement for it, but otherwise I quite like her style of playing the prelude. It's amazing how many different ways people find to play this apparently simple music.