There was an Outer Limits, Twilight Zone, or Night Gallery episode (definitely in color) where a town didn't allow music or singing because they believed it would bring the monsters out.
The newcomer to the town asked if anyone had ever seen the monster. To which they all responded "no because we don't allow singing". "Maybe you haven't seen them because they don't exist". Of course he gets everyone to join in a song which promptly gets everyone killed as the monsters descend upon them.
I can't remember the name of this episode or even the series. Does this ring a bell with anybody?