If obsessively uncovering secrets through ancient sound is our job here, then this is very much on-topic. It’s not exactly an obscure occult text, but The Lost Stradivarius is a great ghost story anyway, Falkner pitching it at a sweet spot somewhere between The Great God Pan and the works of M. R. James. It’s a long short story or perhaps a short novella, in any case worth an hour or so of your time.
The Lost Stradivarius
The Lost Stradivarius (free text at Project Gutenberg)
The Lost Stradivarius (free audio at Librivox)