MP3 Player Shield Music Box
Contributors:
HelloTechie
HelloTechie 
Circuit Diagram
You will need to put the reed switch near the opening doors of your box/case, and a magnet on the other side, so when the box is closed the magnet and the reed switch are right next to each other. Based on your project, you may consider different types of switches instead of a reed switch. If you have a smaller box, you might want to check out the other sound modules we carry. For example: an Audio-Sound Breakout - WTV020SD with an Arduino Pro Mini 3.3V as the development board. Please keep in mind when changing the parts to get the appropriate motors and power supply.