What you will need:
Electric guitar or any instrument with electrical pickups (I used a bass)
An amp and a leed to plug the guitar into
A metal ruler
Step 1: Assembly
Get your metal ruler and lay it on the guitar so that one end is on the bottom of the fretboard and the other is on top of one of the pickups like in picture 3.
You may want to put an elastic band around the ruler and the neck to hold it there.
Plug in the guitar and your ready to play!
Step 2: Playing!
Then gently tap the other end of the ruler against the pickups and it's as simple as that!
To change to pitch of the noise you can press the ruler down in different places.