Box that opens with music

Hello everyone,
I want to make a present for someone that loves to play Musical instruments.
So I want to make a box that can be opened with a specific note (frequentcy).
So I need an arduino and a small mic and a small motor.
But how can I transfer the sound of a specific note from the mic to the motor moving?
Thank you all in advance!

Have your Arduino detect the frequency of the tone (which of course is not trivial - you probably heard of overtones and so), and if the correct frequency is detected activate a motor.

The first is the hard part. Start there. Activating the motor (as it's to open a box I'm thinking of a servo) is the easy part.