Sorry, 'sme again
WLD
"If you find the humanity in a piece of music, maybe that's just another word for folk, isn't it?"
Not for me it isn't.
The term was created to describe song, music, tales, customs with specific origins, creative patterns, transmission etc.
Apply it in the general sense, as you propose, and it ceases to have any meaning - I find much 'humanity' in Beethoven's string quartets, or Goya's war paintings, or Zola's short stories, but I would never describe them as 'folk'.
Jim Carroll