Ed, while I understand your main point and respect the way you work and think, I'd question how clear it is that Rembrandt was painting over either mistakes or "mistakes." I don't paint, but I've lived with painters and watched many such artists at work. The painting over seems often to be part of a process, a building up of depth on the canvas and a way to allow under colors to influence over colors. Just like, as I've said above in this thread about RAW usage, post processing is simply part of a process for me and not something I use to cover over or deal with mistakes (even though it can be used that way). "Mistake" is a term of judgment that I don't think necessarily applies to artistic process. "Mistake" implies something is wrong, which means something else is right. I don't think art is about right and wrong. I think of art as living, so in that sense the composer who revisits a passage and changes it, whether before or after publication, is allowing his art to grow. This is how I think of the painter who covers over a portion of his painting. Growing and changing does not imply the previous state was a mistake. The composer and painter may not have made mistakes the first time. They may simply see and hear differently now or have different needs or desires now. As for dissatisfaction driving art and invention. Sure! Good point. I'll wager that art and invention also drive dissatisfaction. Art is not always the passive partner . . .