Flute

Flute
In Harry Potter and the Philosopher's Stone for Christmas Hagrid gives Harry a flute. Later on Harry realises the suspicious coincidence in Hagrid wanting a dragon more than anything else, only to meet a stranger who had one to give him. He, Ron, and Hermione run to ask him about the man who gave Norbert to him, and he says he never saw his face, and that the man was dressed in a cloak. Hagrid also mentions that they talked about Hogwarts and Fluffy the three-headed dog. Hagrid lets it slip how to get past Fluffy by playing music, which sends Harry, Ron and Hermione off. After finding out that no one will do anything to help they go to the third floor corridor at night under the invisibility cloak andHarry plays the flute which causes Fluffy to fall asleep.

Harry Potter and the Philosopher's Stone (movie)

 * In the movie Hagrid has the flute and it doesn't mention Hagrid getting Harry anything for Christmas
 * Also that instead of a flute there is a harp which is already playing when the trio get there
 * In the movie it gives a reason to believe that someone had already been there by Fluffy being asleep but in the book Fluffy was awake.