Rather than talk about work, here’s something about D&D.
The 2nd edition Monstrous Compendium describes how on full moons Death Knights will sing about their tragic fall from grace. That’s so Ravenloft.
BUT consider a death knight is the armored nigh skeletal cadaver of someone who was a knight in life, not necessarily someone who could carry a tune in a bucket helm.
So they probably sound a little like Tom Waits, only badly off key, muffled, and with weird echoes.