@Don Corleone: Traditional Arabic music does not have scales. Only those Arabic songs which borrow heavily from Western music use scales. Real Arabic music uses maqqamat, which are very different from scales. They are impossible to play on a guitar or any instrument Opeth has used. Trust me, I did an entire project for my Arabic class on this subject. ~_~ Arabic music theory is fucking crazy. T_T
Anyway, my all-time favorite Opeth solo is the second solo in Windowpane. God DAMN that solo cries. If all Damnation had was that one solo, it would have been worth buying still. I have my doubts that they'll ever record a better solo. I LOVE playing this song.
My second favorite Opeth solo would have to be the first one in Godhead's Lament. I love the way it sets up the melody for the 'Searching my way to perplexion' verse. Really beautiful.
I love the solos in The Funeral Portrait, too. These are the only other two Opeth solos (besides Windowpane's) that I know how to play. It was actually the second solo from this song that convinced me that I ought to practice sweep picking again.