Working on a simple door lock this is my first project on an Arduino platform. My aim is to build up a door lock unlockable by playing a short melody on a one-octave piano keyboard. I think the idea is cool!
I'm thinking at everything, but I can't figure out how to make Arduino move something (which in my case would be the proper door lock). I thought about a little motor, but I don't know if it is or not  feasible...
To be clear, what I want to do is a simple door lock like this 
(or even simpler) being moved from an Arduino program. How can I do that?
You want a solenoid.

Looks like people sell ones which are specifically made for door locks.