Ed, my study of the roots of jazz indicated the early musicians did, in fact, play improvisations of traditional songs - church music and marches, mainly. The musicians may, or may not, have been able to read music, but they certainly learned the standards of their day. They played over a structure. They had to - you can't create art from anarchy.

I believe photography is the same. You have to learn enough about your camera and materials and their structure before you can create art. You can follow the rules or break the rules, but in breaking them, you create your own new rules.
juan