In a 1986 interview with Guitar Player
magazine, Alex Lifeson explained the sounds in the opening: "That's just the Ibanez HD-1000 Harmonics/Delay set at an octave above with a little bit of modulation. The harmonics level is set at about 70, the direct is set at the full 100, and I was on the middle pickup on the black Strat. I used left-hand finger-pulls. After that, it switches to a much crisper tone, and to do that in concert, I just switch to the back pickup."
Mike - Darkside of the Moon, for all above