Yep. Singing killer space fungus.
I'm trying to find a science fiction novel that scared the bejesus out of me when I was a kid. This book was one of those paperback novels from the '60s or '70s. It featured a plucky teen who'd stowed away on a spaceship and his lovely girlfriend. The monster was a man-eating fungus that had grown in the ship's ventilation system and lured its victims into its lair by singing.
Google hasn't been able to help me out with this one so far. If anyone has read this book, or knows of a database of '70s sci-fi, please let me know.