Watching the players jump is a beautiful thing
Buddy Hackett: Now you have to ask me, what’s the secret to comedy?
Johnny Carson: Okay, what’s the se–
Buddy Hackett: TIMING!
When I was running my tabletop Cthulhu game, I occasionally set up phone calls to come in at particularly tense moments…often just as I said the phone rang…or I would drop a book or hit the table from underneath when everyone was whispering and quiet. I once waited til no one was looking at me, then screamed…or played a glass-breaking sound-effect through a hidden speaker. Watching the players jump is a beautiful thing.
He also had some great ideas about using darkness, camouflage, and even a (fairly graphic, by the sound of it) fake dog corpse to freak out the players.
But the sound stuff caught my ear. Not because the sounds he used were really complicated, or required lots of specialized equipment –they weren’t and didn’t– but because they were dead simple and relied entirely on timing. One of the key things about his approach (it seems) is that, as a GM, he’s tuned in to where his players are at emotionally, and knows just when to hit the sound cue for maximum effect. Ever play a sound you thought was going to be totally awesome and freak everybody out, only to find half your players missed it because they were still discussing the last roll, or wondering when the pizza was going to show up? Sure, you can play stuff again (and for expository sounds you may want to), but it will never have the same impact.
The right sound is only the right sound if it’s played at the right moment. Timing is everything.