Katy Perry Voice of a Baby Silencer

8/6/2014 12:15 AM PDT BY TMZ STAFF

Got a crying baby … get Katy Perry! Her hit, "Dark Horse" turns out to be a highly effective lullaby … or at least it was for the toddler melting down in a viral video that even Katy herself noticed.

Watch how the song makes a cute kid instantly act like a happy drunk girl … in full-on club mode.