It was 1998 and the song "Believe" by Cher was rocketing up the charts.

A strange metallic warble effect applied to Cher's voice made the song incredible popular when the public latched onto the effect and drove sales into the stratosphere.

At the time, Cher and her producers claimed the effect was produced by a vocoder, a voice modulation device that had been around since the 1970's. In fact, the effect was produced by a piece of software called AutoTune, and this bit of software was about to change the music industry for ever.

Created by engineer and part-time musician, Harold "Andy" Hildebrand, the software was initially designed to analyse underground sound waves in an attempt to pinpoint hidden oil reserves at his employer, Exxon.

During a social dinner one evening, the wife of a friend challenged Hildebrand to create software that could make her sing in tune. Hildebrand took the challenge seriously and, using the base software from his Exxon days, created AutoTune.

The software was able to correct the pitch of any music note without damaging the rest of the track. Previously, correcting pitch was a case of speeding up or slowing down the entire recording.

After leaving his employer Exxon, Hildebrand started Antares Audio Technologies, which wrote software for the music industry. AutoTune was primarily used by recording companies to correct the odd off key note from studio recordings, but soon other artists were exploiting the software's capabilities to create strange voice effects such as those found in Cher's song.

And who could blame them? "Believe" became the 52-year old singer's greatest hit and one of the best selling singles of all time.