I had a number of dreams about piano, ranging from very joyous to very upsetting. In my favorite one, I was in a room with a bunch of relatively famous pianists (Emanuel Ax is all I can remember, and Yo Yo Ma was next to him but he ain't a pianist), and there was an old upright sitting on the side. I sat down and stared at the keys, thinking of what to play. Then my friend (who also plays piano) came and sat down next to me, and said we should improvise something. I said we should improvise a fugue... and so I started with a nice theme in C major, after which my friend joined in. So we played a 5 or 6 voice fugue, but when I realized I was actually improvising such a huge fugue in my head, I woke up. I scribbled down the theme, but I could never make anything of it, sadly. I'm no good at composing or improvising, and I have no idea how I was able to pull off such a feat in my dreams. But it was quite an exhilirating experience for all the moments it lasted.