At Banjo Camp North, Peggy Seeger told me ( I THINK with a twinkle in her eye) that there were only eight tunes.

I said something like, "Yeah, and there are only five novel plots, too! Only by picking out extremely generalized plot elements."

She said, "You don't believe that?"

"I sure don't!"

Reminds me of some famous playwright's description of the plot of the ideal three-act play:
   Act one:    Chase your hero up a tree
   Act two:    Throw rocks at him
   Act three: Get him down from the tree

On that level, maybe there are only four (or eight) tunes. I'll describe one:
   State theme
   Elaborate theme
   Restate theme
On that level, maybe!

Dave Oesterreich