Detecting movement without movement detector? Am I dreaming?

I just saw this post where this user build a lightsaber using arduino and a sound module that responds to movement and impacts to make the sounds of a lightsaber (wing and clash) BUT HE USES NO MOVEMENT OR IMPACTS DETECTORS!! HOW?? is that even possible? I read all the entire post and it seems like he just used those 2 components to make that... how is that possible??

Just in case I bought an accelerometer to make my lightsaber so I have a movement sensor to add to my arduino... but, can I just save it and not use it??

thanks

http://forum.arduino.cc/index.php?topic=261980.0

Read reply #17 of that thread.