I didn't do that much actually....I did backing vocals on 5 or 6 songs + a solo and some nice guitar vibes of "Arriving somewhere...". I did a full on metal solo for that song as well that was scrapped because it was too metal for them, haha, or maybe I sucked, I don't know which.
Steve wanted to use my voice as he (and me too) likes the textures of having multitracked harmonies by at least 2 different voices, that's why he sings on Opeth albums as well. Just listen to "Because" by the Beatles and you'll know what I mean.
Mike