beat activated light switch

[Peter_F]

so i was wondering if anyone knew of a good design for a box that would take, say, recorded music, and find the beat and switch normal 120V house lights on and off to it (basically pulse on the beat). I saw a design a while ago with just an input run through a lowpass filter that operated an optoisolated switch. The switch controlled the line current. Has anyone heard of or seen a similar setup? There are numerous ways to do this i know, but this was a simple, effective, and cheap alternative.

[zachary vex]

basically you're looking for one channel of a color organ if you want to have a light go on and off with the kick, or kick and snare.  if you do a search for
color organ schematic
in google, you'll find lots of possibilities, like this simple circuit: (my guess is this one responds to the loudest things in the mix)

http://www.aaroncake.net/circuits/corgan.htm