Originally Posted by: JeffS65It called a Talk Box

Here's what he used:
http://www.jimdunlop.com/index.php?page=products/pip&id=287

In short, it is used like a guitar effect and would be in your 'stomp box' chain with the nylon tube running up to the microphone as you see in the vid. So, when you step on the box to turn it on, it would stop the signal from going to the amp and turn on a speaker internal in the box unit. That would send the signal through the nylon tube strapped to the mike.

So, with the tube in your mouth, the sound 'spills' in to your mouth and you mouth out things as if you were speaking but the 'noise' is provided by the tube. As you can guess, the microphone is picking up the sound.

So, it's really more of a singing your guitar sound only without using your vocal chords but with the chords and notes played on your guitar.