Here’s a clip of Boris Karloff, showing off his vocal chops on the Rosemary Clooney Show in 1957. It’s a duet with Rosemary in the middle of a Little Red Riding Hood skit—Boris is the Big Bad Wolf, disguised as Grandma. (Length: 2:32):
He’s got a great voice, though the song seems slightly creepy by today’s standards…
You can also hear Boris singing a children’s song on the same show, here (from a
video of the entire show; the link should start playing 18:43 in).