Wendy Carlos was not the first person to use “Dies Irae” as a horror theme. It was done previously in The Screaming Skull.

Yes, that The Screaming Skull—the one from 1958, that elevated the skeleton to its rightful high place in the domain of monsters. (The Screaming Skull and the Emergo™-enhanced House on Haunted Hill (1957) were the first to utilize the Living Skeleton—the scariest of all the classic monsters—as the film’s primary antagonist.)

Here are other films that “quote” it without using it as a title theme:

Metropolis (1927)

The Screaming Skull (Jan 1958)

The Return of Dracula (Apr 1958)

Poltergeist (1982)

The Hunchback of Notre Dame (1996)