Inside Borgin & Burkes you will find many dark replicas, including a hand of glory that will move when you get close. Once you make your way to the counter, find the vanishing cabinet near the front. If you listen you can hear the bird chirping inside.
There are many spell locations in Knockturn alley, but when you get to the shrunken heads listen as they will sometimes sing the song from Jaws. A shoutout to the Jaws ride that used to be there before it was torn down to make room for Diagon Alley. Also keep your eyes open as there are tons of detail such as moving pictures, spiders, and look up at the clouds in the night sky.
So make sure to visit Knockturn Alley, I have heard of some people who missed it because they didn’t bother to look down the dark alley ways, and this is something you will not want to miss.