Does "malefic rune", possible typo from "tune" in the context?

I have been reading a story by Robert Bloch – The feast in the Abbey. I just cannot see how the "rune" can be correct in the following:

As I thus mused there fell upon my ears the sounds of sonorous
chanting that swelled symphonically from somewhere far below. Its
measured cadence rose and fell solemnly as if it were borne from a
distance incredible to human ears. It was subtly disturbing; I
could distinguish neither words nor phrases that I knew, but the
potent rhythm bewildered me. It welled, a malefic rune, fraught with
insidious, strange suggestion.

Should not "tune" make sense? However, all references I found read truly "rune", but again all could be using the same, corrupted OCR…

Thanks a lot