I think he sounds like a voice synthesizer because the owner probably "trained" the raven to say nevermore by letting a computer program repeat that word occasi

I think he sounds like a voice synthesizer because the owner probably "trained" the raven to say nevermore by letting a computer program repeat that word occasionally over long periods of time. Thus he learned to mimic the synthesizer sound, not a real human saying it. You can also hear the bird repeat some notification sounds a "waka waka" sound that sounds like Pacman.