What's the problem with copyright? Assuming the rights owner can be found and midi transcriptions made of the piano rolls, why would it be legally any more comp

What's the problem with copyright? Assuming the rights owner can be found and midi transcriptions made of the piano rolls, why would it be legally any more complicated than publishing sheet music? Of course any public performace would require royalties, as would shipping the midi files as demos when selling a piano, but that's kind of the whole point of copyright law.