Auto-Tune
Auto-Tune is a particular brand of software (there are others) that can alter pitches in a vocal performance. In a nutshell, it’s like “Photoshop for human voice”, as Time journalist Josh Tyrangiel put it. It can correct a sharp or flat note so that it is pitch-perfect. It’s also used as an effect to make a vocal sound somewhat unnatural or robotlike–the first notable instance of Auto-Tune used in this way was Cher’s “Do You Believe” back in 1998.
Auto-Tune is much used in pop (including pop country) music these days; most of the time it’s pretty obvious because the vocal sounds too perfect. Interestingly enough, it’s difficult to get the robotlike effect unless the pitch of the vocal is way off; this of course makes one wonder how many pop stars can actually sing these days. It’s also notable that Auto-Tune can be used in live performances as well as recordings; some artists have admitted to using it in this way as a “safety net”. Auto-Tune could even make Alfalfa sound like a perfect singer.