A Lulling Song

Exploration Stage: Bright Sunroom
From: Conductor
Description: I strained my ears to see if any monsters were creeping up on me... but I almost fell asleep! It seems someone is singing. Can you hear it? It sounds like a lullaby. That’s why I got sleepy. I’m going to find out who’s singing.
Completed: That’s quite a trick! The Doorkeeper’s mechanical nightingale is wearing a nightcap and whistling a lulling song. Why did the Doorkeeper reconfigure his bird? Does he have insomnia, or what?