Watch the David Gilmour online guitar lesson by Jeff McErlain from Kings of Tone
Here is one of those fun little pedal tricks that I am sure Gilmour stumbled upon by accident. I have this picture of him plugging in his pedals and turning on the amp and suddenly this loud howl nearly deafens everyone in the room. Then he thinks "hey, I could use that!". That's the way it happened in my head so I'm gonna stick with that story. Oh yeah, when you do this make sure your amp volume is way down, it is LOUD.