Nikolo Paganini was known to practice violin without actually touching one. Same goes for composing. He (allegedly at least) used to conceptualize in his mind h

Nikolo Paganini was known to practice violin without actually touching one. Same goes for composing. He (allegedly at least) used to conceptualize in his mind how his hands would move for each part, and would master those movements, even though he wasn't actually doing them. It greatly played into his reputation of having made a deal with the devil, because people only very rarely heard him practice or compose - he just went ahead with new content seemingly out of the blue, but in reality put a lot of work into it. It sounds very similar to what Nikola Tesla often did.