The most genuinely chilling 'love song' so to speak, I've ever heard is Bartoks Bluebeards Castle
Love this opera. It presses all those dark psychological fairytale nightmare buttons.

Through the sixth door in Bluebeards castle, Judith finds a lake.

And says:
"I can see a sheet of water, white and tranquil sleeping water.
What is this mysterious water?

Bluebeard replies:
"Tears, Judith! Tears!"