We should think about nightmares. I had a recurring nightmare when I was about ten, much too precise for me to have imagined it--so precise, in fact, that it took a long time to figure it out. It was about tuning, actually. In fact, it was about the difference between the tonic pitch in a Bach English Suite and the solidity of the tonic in a Chopin piece I was playing at the time. The Bach was, of course, not written for the piano. I didn't know that. I knew, however, that I could not "find" its pitch. The Chopin "Raindrop" Prelude, written with the piano in mind, was security itself.