When it comes back at the end of Duke's Travels, it's different somehow, it has a different meaning. The first time, we've been introduced to Duke and his loneliness and his obsession with the Duchess, and then the Guide Vocal shows up and tells him that from this point on, he's on his own. Damn, it's a cold world, ain't it? Now, the story is pretty sketchy to begin with, but near as I can tell, "Turn It On Again" is something of a bright spot in the story, with Duke understanding that he's alone, but at least he gets some pleasure from the TV and the radio. "You're just another face that I know from the TV show, but I have known you for so very long, I feel you're like a friend." Then after Duke's Travels, the Guide Vocal returns to reinterate Duke's crappy situation. He's leaving (again?) and Duke will (again?) be alone. And this time, he really means it.