"Entertainment, like good singing or music, is in the eye/ear of the beholder/listener, is it not?"

Yes. That's why I said, "Just because someone is deliberately setting out to entertain me does not mean that I would be entertained by them. And vice versa, I could be propping up the corner of a bar and be hugely entertained by a couple of folk in the corner playing tunes just for themselves."

But it interests me how beholders of specific ears form fashion cliques. Such people club together and begin to sound the same and wear the same clothes. It interests me because I'd like to understand where or when a fashion clique can become regarded as a tradition

And I still don't understand the relevance of amateur, semi-professional and professional?