"What's diegesis - dictionaries didn't help?"

The word roughly means 'story world', one created by the teller. A fiction so apparently complete it draws the listener in so he believes the tale. The beguiling story here is mysterious, unknowable individuals created a music that was adopted seamlessly by society until an apocalypse (industrial, communications or in some other way post-Edenic) atomised a nation until rescued by seers. Research with a dusting of the numinous if you like. Tweedy shamen capturing the dying flames of a disappearing world backed up by a committee who bought the idea.

You couldn't make it up, but someone did.