WARNING: The following contains major spoilers for DC Horror Presents: The Conjuring: The Lover #4, available now from DC Comics.
In the world of The Conjuring, one of the most mysterious relics has been the music box, which was first seen in the first movie. The item came to light when Lorraine Warren checked it out at the Perron home, knowing the family was being haunted by a demon. There, she played it and saw a young boy in the mirror's reflection, confirming dark spirits were surrounding the blighted residence. Now, The Conjuring: The Lover #4 offers more insight into the item's demonic power, and it paints a bloody, horrific picture that blurs the line between nightmare and reality in the back-up story, "Tales from the Artifact Room: The Sleeping Song," by Ray Fawkes, Christopher Mitten, Brennan Wagner and Becca Carey.
In this story, a young pianist, Nicole is grieving the loss of her baby. She admits her child constantly cried but calmed down when she brought her to the piano to play.
When her husband comes home, they argue, with her husband frustrated that Nicole missed rehearsal and that he had to fill in. He thinks she's becoming an alcoholic as Nicole tells him she thinks he killed their child. She's been driven mad by the toy box and its song, which has twisted her mind with its constant noise. However, the man doesn't know the kid she's seeing in the reflection -- the same boy from centuries ago apparently -- has driven the woman mad.
She grabs a knife to avenge her dead child, stabbing the man, not realizing the boy put hallucinations in her mind. He wanted her to think her significant other strangled the kid for crying too much. Under the impression that she's serving justice, she attacks and ends by sitting down, spending time with the box as it plays more music, implying the box feeds on innocent souls.
It's never confirmed if the baby died of natural causes, but the boy could've tempted the woman to murder her baby herself. The box, after all, was scaring the kids in the Perron home. Ed knew it had a dark, enormous power inside, which is why he kept it in his storage room with other macabre trinkets.
The box didn't factor in much in subsequent movies, but this story hints that the box could have corrupted the kids. If Bathsheba had not been haunting the family, the box could've hurt Roger and tried to possess Carolyn, maybe it could have driven the mom to enact violence herself. From Nicole's reaction, the sinister boy knows how to work his stronghold as she doesn't even care she's sitting in her husband's blood at the end.
She's enjoying the music, comforted by memories of her child and not ever wanting the box to stop turning. She does realize she can't tell what's real anymore, as she senses this song isn't something she wrote. Nicole admits it's really his song, but it's the ultimate curse since she can't stand the loneliness and grief the silence brings without her infant.