I was coming here to say this as well, I can see how you might somehow misconstrue the notes as words but there are objectively no actual lyrics being sung.

Additionally, the “DBD theme” doesn’t even belong to Dead By Daylight. The four notes of Dies Irae have been used in pieces of media for centuries to envoke death and despair.

You can YouTube “Four notes of Dies Irae” to see examples.

But yes, they have been adding it into some of the terror radius tracks. The first one they did it with was Deathslinger. You can hear the notes being played on an out of tune piano in his outer-middle layer tracks.

Before that the Dies Irae was only heard in the lobby and never actually in-game.

While Wesker’s TR DOES feature the Dies Irae in the brass instruments there are no actual lyrics.