Imagine the conversation that came before this response? Response: In the background Joseph is working on making a yoke.
A 2 person dialog:
Person A: What does Mary do with a feather duster?;
Person B: Mary looks up from her book to take a peek at the sleeping child under the crib curtain (Dutch: "klamboe").;
Person A: What is Joseph doing in the background?;
Person B: 