In the middle of the Defence Against the Dark Arts class there is a projector. Cast Depulso on it and look at the screen. You will see some pictures of a witch with a flower, and then... Da Vinci's Homo Quadratus! if you take a closer look, you will see... more
Go to the clock tower at Hogwarts. Go to the top where to you see a whole bunch of large bells. Ring, using Depulso, the 4 or 5 bells near them on the ground. The large bells will ring.
They play the Hedwing's theme!