You will need:
1. An empty CD box
2. 3-5 Paperclips
3. Some wires
4. 1/4" jack/adapter with cable
5. Duck tape
6. Plasticine cat to oversee you activities
Step 1: Attach paper clips to make it bouncy
2 .Put a bent paper clip inside, as shown.
3. Tape it to the box with duck tape.
Now if you try to close it, it will bounce back, like a pedal. The problem is that it will snap closed if you press hard enough. We resolve this problem in the next step.
Step 2: Make it a pedal
2.Now press on the cover and see if it bounces back with enough force.
3.Add more paperclips on the inside to your satisfaction.
Note that you probably won't get enough force to sustain the weight of your foot, unless you have really hardcore paperclips.
Step 3: Attach the wires
2. Firmly attach a paperclip to each wire by twisting, wrapping around, tying a knot, etc. (just don't solder =)
3. Now duck tape the wires with paperclips to the CD box so that the paperclips touch when the box is closed, and don't touch when it's open.