A surprising amount of CSS development would probably fit the bill as well. So many times I've produced unexpected results that looked just as good or better than my original intent.
"Hey, wait a minute, that wrong note actually sounds really cool there. Let me try to build upon it."
https://www.youtube.com/watch?v=cK5G8fPmWeA&feature=youtu.be...
"Oooh that's neat... Not sure how I did it though."