I need a tranquilizer dart

There is a small, unsupervised child who is apparently intent on calling down the moon by banging on the metal steps of my apartment building with a large red plastic whiffle ball bat. She is also chanting. Or is it singing? There are no words, at least none that I understand, and apparently no tune.

How she hasn't woken the roommate, I don't know. Maybe I ought to go wake him, just so he won't worry.