I can't have a product that is built using these keys, can I? I assume Korg will not be happy about it.
(I'm assuming at this point you are trying to set up a first prototype or making something you can assemble yourself in a small run)
If you will just make 1-2 copies for your internal use, most probably nothing happen, because in legal practice exists negligible case, where not worth considering sue you.
But if you will show copies on public, upload 3d model on your site, and/or try to sell them (make ads, other marketing, and yes, opensource copy of patented things also prohibited), on some moment they could make decision, this is not negligible and will sue you.
To avoid such things, you could try to find their patents and make your own mechanics with other geometry.
Also, patents are not forever, usual max term approx, up to 70 years, and than it become effectively public domain.
So you could copy mechanics of some old piano, or expired patent.
All business is really circle: begin -> try to make -> try to sell -> measure income -> decide if possible to continue (or if worth) -> if decide, return to begin.
Nobody could tell you if it worth, without try. To be strict, exist people, who know everything, like taxi drivers, but for some fundamental reasons, they don't use their knowledge to earn money and got some better life.