arrete wrote: Getting better at a musical instrument seems to grow like a step function rather than a smooth line.

Steps to competence.

Unconscious incompetency. You don't yet know how bad you are at something. After investigation comes...

Conscious incompetency. You know how bad you are, but at least you know the steps to take to improve.

Conscious competency. You've learned enough to be competent, but you've got to consciously think about doing the task well while you're doing it.

Unconscious competency. You're now so competent that you don't even have to think too much about what you're doing to be good at it.