Simple solution for adding sound to your pneumatic prop

This project was something I did before I really understood how to use micro controllers & their shields. I wanted to build a Halloween prop that is usually referred to as "Trash can trauma" but I had my own concept in mind. Instead of using a trash can I wanted to make a jack in the box display.The project has gone through several updates but what I plan on focusing on is how I added sound to it. It works so reliably I Haven't bothered to update the audio portion of the project.
 Since this is a project that I put together some time ago There really isn't a step by step process outlined here but the sound portion is something that is really simple & can be used on many different projects. I will try to explain enough that just about anyone could build the same project if they wanted to. 

Step 1: A word of caution

 I would just like to make anyone, that doesn't already know this,aware that air pressure can be dangerous. If you have any doubts about your project, err on the cautious side. When testing, use very little pressure & when setting up use only the amount of pressure needed. A broken hose can swing like a whip and a cylinder can exert enough force to break bones & knock out teeth. DO NOT TAKE THIS FOR GRANTED!!