NEW YORK -- As he prepares for his upcoming farewell tour, Barry Manilow knows something is missing. In an exclusive interview with ABC News' Chris Connelly, the singer opened up about how being diagnosed with lung cancer and undergoing a left lung lobectomy has altered his voice. "My voice -- I don't know whether it's coming back," the Grammy winner said in an interview that aired Monday on "Good Morning America." "I did my first sound check about a month ago and I didn't sound like me at all.