Those who love recorded music well remember the voices Frank Sinatra, Sammy Davis Jr, Perry Como, Dean Martin, Karen Carpenter, Dionne Warwick, Mama Cass Elliot, and Etta James. Those voices, popular during the nineteen fifties, sixties, and early seventies, were pure and practiced. Their lyrics were delivered clearly and with feeling.
Their voices were recorded on primitive studio equipment. Backing them were woodwind, brass, string, and percussion instruments played by talented musicians. The voices and instruments we heard on their vinyl recordings were the music as they played it. No electronic enhancement equipment was yet available.
Then, along came the age of electronics in recording studios. Electric guitars began to replace acoustic guitars. Electronic drums replaced real drums. Mixing boards created sounds that the instruments had not and could not.
Finally, about 1990 the pitch correcting microphone was introduced. Almost suddenly, it was no longer necessary to have a great singing voice sound great; pitch correction would more than cover a singer’s vocal shortcomings.
Many may not know that these devices exist. Their use is common and can make a star of someone who otherwise could not string together three notes. A modern recording studio can make an inadequate voice sound almost sensational. Overdubs, back-up singers and recording studio sound board electronics make a record sound great when the actual voice of the performer never could.
The paragraphs below are quoted from Wikipedia.
The most common use of pitch correctors is to fix wrong intonation (tuning) of notes sung by vocalists in popular music sound recordings. The use of pitch correction speeds up the recording process because singers do not need to keep singing a song or vocal line and re-recording it until the pitches are correct. The pitch correction software can correct any pitch errors in the singing without the need for overdubbing or re-recording.
While pitch correction is most associated with fixing vocal intonation errors, it can also be used to fix intonation in recorded instrumental parts such as violin, cello, or trumpet.
Pitch correctors are commonly used in music studios to add the sound of vocal harmony to certain sung words or phrases without re-recording those lines again at the necessary pitches or using backup singers. Depending on the model used, various vocal effects can be added, and better-quality devices can be adjusted to allow expression to remain in the music. Some pitch correctors can add vibrato.
While pitch correction devices were initially designed to produce natural-sounding effects, producers discovered that by setting extreme parameter values, unusual effects could be obtained. Pitch correction devices became popular in the late 1990s as a distinctively electronic, vocoder-like voice effect. A notable example of Auto-Tune-based pitch correction is the Cher effect, so named because producer Mark Taylor originated the effect in her 1998 hit song “Believe.”