This Instructable has been entered into the DIY SoundHack Contest and the Pocket Sized Electronics Contest! Check it out and vote if you like what you see here!
Here's a clip of what it sounds like (I'm an awful singer... but it gets the point across).
Step 1: Materials and Tools
1 x Altoids Tin
1 x 2-Way Toggle Switch
1 x 1/4" Phone or Audio Jack
1 x Piezo Electric Doorbell Buzzer (You could also wire a condenser mic element, but those require power. Go with the Piezo for more distorted grit!)
Electric Drill or Drill Press w/ Bits
Hot Glue Gun (optional)- Any kind of glue will work.
Step 2: Preparing the Tin
Step 2) Put on your safety goggles.
Step 3) Drill a 3/8" hole into the right side wall of the tin (this will be the bottom of the microphone when holding it). This is where your audio jack will be mounted.
Step 4) Drill a hole just large enough to fit your toggle switch of choice on the left side wall of the tin (this will be the TOP of the microphone when holding it).
Step 5) Drill a pattern of small 1/8" holes in the face of the Altoids tin (where the logo is). You can make the pattern look however you'd like, but make sure you have enough holes to allow for unimpeded sound travel to the condenser mic element).
Step 3: Wiring the Components
Step 4: Mounting the Components
Step 2) Glue the condenser mic element (or piezo buzzer) to the inside back wall of the tin. Make sure you center it with the pattern you drilled out on the top surface of the tin.
Step 3) Close the box. You're ready to rock.
Step 5: Rocking Out
Good luck out there rockstar!