Basically, you're still sitting there using just the muscles of your hand, really. Of one hand, actually. It's another example of the transfer of literacy to making music because the assumption is that everything important is happening in your head; the muscles are there simply to serve the head. But that isn't how traditional players work at all; musicians know that their muscles have a lot of stuff going on as well. They're using their whole body to make music, in fact.
Brian Eno