Most ribbon controllers are linear, but the one on the Otamatone behaves like a guitar or a cheap theremin, with higher notes closer together. Can it be made linear?
To quote Wikipedia,
The ribbon controller is deliberately delinearized to resemble a guitar, so there is a shorter distance between higher notes than between lower ones. - https://en.wikipedia.org/wiki/Otamatone
Basically, they're doing it on purpose because it's how most intonation-based instruments behave. You'll notice that people who play string instruments may be better at playing the, uh, whatever the Otamatone is. I don't really want to call it an instrument, but in light of evidence, I must say that it is fairly capable. ;-)