This guy is crazy! He modded this organ to sound like a NES/Commodore 64 so he could play classic chip-tunes live. YouTube - The Chipophone!
Pehaps the sound is being recorded directly from the device or a microphone right by the keyboard, while his voice is being picked up by the mic on the camera? Or the Chipophone is really loud.
That was so edited. When it goes from the organ to him speaking you can hear the pop of the white noise in the background kick in. You wouldn't hear that if it was actually being played.