"The Real Song for the Deaf", which is essentially Track 0, is located in the pregap of Track 1 as a hidden track. The hidden track can be found by rewinding the first track to roughly -1:33. A voice comes on and says: "Huh? What?" and a pattern of low-frequency bass plays and modulates for the rest of the song.
This track [...] is difficult to listen to on all but conventional CD players. Most software CD players do not allow rewinding of this nature, and most MP3 "ripping" software will not include the data.
This is a pregap track, not an unlisted track at the end. To hear this one you need to rewind the first track backwards until you get to the pregap track beginning.
That utter bastard made one side of Lazaretto play backwards: you have to put the needle in the center of the record and it spins out to the edge. First time I tried to listen to it I was very high and it was hell.
This had been done before. Techmoan on YouTube did a video on a symphonic piece that was put on vinyl backwards. It's something about how the needle travels slower at the center increases the possible dynamics vinyl can reproduce
Dream Theater did this for their entire album Octavarium. Every song has hidden parts, but I think every streaming service has included them into their respective songs