Watching Waters/Gilmour collaborate with Vocals and Key changes, makes it the best song I've ever heard. They start the song in a descending minor progression with Waters' vocals following the sinister path as if he were a evil Doctor offering to ease the pain to his patient.
Next comes the chorus sung by Gilmour as the patient. The music changes from dark to light, minor chords become Major and the song almost starts sounding Angelic, although the lyrics lean toward a heartbreaking sadness with "This is not how I am".
Then Gilmour starts the first solo playing over that Angelic Major sound which makes Waters intro into the second verse even more tragic.
Then Gilmour starts the the final chorus over the Angelic progression with one of the saddest lines this writer has ever come across, lyrical or otherwise; "When I was a child, I caught a fleeting glimpse, out of the corner of my eye....I turned to look, but it was gone; I cannot put my finger on it now, the child has grown, the dream has gone"..
Then he leads into the second solo, but this time plays over the descending minor chords of the verse. Arguably, one of the greatest guitar solos in rock history. How can I explain this in words??? It was like a colony of Taranulas crawling up my spine!!!!!!!!!!!! Brilliant..................