Its main purpose is to slightly bend sung pitches to the nearest true semitone . Auto-Tune can also be used as an effect to distort the human voice when pitch is raised\/lowered a lot . While its main purpose is to slightly bend sung pitches to the nearest true semitone ( to the exact pitch of the nearest tone in traditional equal temperament ) , Auto-Tune can be used as an effect to distort the human voice when pitch is raised\/lowered significantly .