Not too sure if this post belongs here, but I just thought of something that always gives me trouble when trying to help folks out. I recently did a couple of live sound gigs for a local band who has decided to bring in a friend of theirs to do sound. They've asked me to come give him a few pointers, as he's being trained "from the ground up." (sounds like a recipe for disaster) One thing I've always had trouble explaining is how a compressor works. It never ceases to amaze me how many musicians (guitar players, esp., of which i am one) and audio/engineering newbies say, "yeah, a compressor makes things louder, right?" So I say, "well, no and yes" and draw out a graph of input vs. output and blah blah blah and eventually realize that all I really did was confuse them. What's the simplest way anyone has come up with to explain this concept to someone who doesn't understand it?