The International Journal of Geriatric Psychiatry has a brief case report of a man who began hallucinating whole operas that would start every evening shortly after sunset.
A 74-year-old retired mathematician had to undergo emergency surgery due to an ischemic perforation of the colon. Three days after the operation, he began to suffer from near complete insomnia and mentioned only briefly that ‚Äòthis monkey music‚Äô kept him awake. His condition deteriorated and 5 days later he admitted, that he heard complete operas at night from the very first to the last chord, ‚Äòand you know how long these operas are‚Äô.
He could not offer any explanation as to where these sounds came from, could not distance himself from his elaborate musical perceptions, had no means of interrupting them, and feared the first notes of another overture (which reliably rang out soon after sunset).
On examination during daytime he appeared tired and irritable, rather uncooperative with poor concentration, but without overt evidence of a severe confusional state. His medical history was inconspicuous, but it became obvious that he was a dedicated opera-lover with a profound musical expertise, which he had acquired over decades of studying scores and librettos in every detail.