When I first tried returning to classical piano after a few years with PD, I could barely coordinate my two hands. I often had a delayed muscular response from one finger or another that translated into mistimed notes. I tried certain pieces of music that seemed hopelessly beyond my ability. Because I only play for my own amusement, I didn't fret too much over it, but I was definitely discouraged. I thought I'd just stay with simple pieces of music that I could master.
After doing that regularly, playing little pieces I had learned as a child or in my teens, I noticed improvement, so I gradually advanced to more difficult music. I had thought nerve/muscle coordination could not be improved, but I was wrong. Now, when I time my medication just right, I get the same intense feeling of getting inside the music that I used to have years ago. For an amateur, I can play reasonably well such things as Chopin's "Berceuse" and "Fantasy Impromptu in C-sharp Minor" and Beethoven's "Sonate Pathétique" and am currently learning Mozart's "Sonata No. 16 for Piano." You'll never see me on the concert stage, of course, but with almost daily practice, I have improved enough to find joy in playing.