In the past, music producers had to manually adjust the pitch of an audio track. In 1997, Antares Audio Technology introduced the Auto-Tune software, which corrects pitch in real-time. Real-time pitch correction allows for use in a live performance and not just in the studio. Since pitch correction software's introduction, the market's top digital audio editing programs regularly have this program packaged together with them.
South engineers mainly use pitch correction to adjust out-of-tune vocals. However, they can also add harmonies to parts of a song without the need for re-recording.
Sound engineers may also add vocal effects during the process. Through the correction software, they can add an electronic effect to voice recordings, which has become increasingly popular since it Cher used it on her song "Believe." This effect is prominent in much of T-Pain's music today.
Two types of pitch estimation exist: frequency domain and time domain. Time domain examines audio signals by looking for repeated patterns. Frequency domain looks at the audio within the frequency domain and implements a transform operation on the signal.
Critics of pitch correction believe that it helps an unskilled vocalist to give an in-tune performance and contributes to manufactured performances and artists. When done poorly, or in excess, the effect can cause a trill in the singer's voice.