Viewers quickly picked up on the use of vocal effects on performers from Saturday's launch show, including Zimbabwe-born Gammu, duo G&S and single parent Shirlena Johnson.
Fans accused the show's producers of "deceiving" the public by using techniques such as auto-tune to resolve weak or poorly pitched vocals.
Reps for the reality series have denied that auto-tune was used, but admitted that alterations had been made during the production process to ensure an "entertaining experience" for viewers.
An official show spokesperson told The Guardian: "The judges make their decisions at the audition stage based on what they hear on the day, live in the arena. The footage and sound is then edited and dubbed into a finished programme, to deliver the most entertaining experience possible for viewers."
Meanwhile, an insider source told The Mirror: "Auto-tune is not used in the live shows but purely for the audition phase. It has always been part of the show for pre-recorded items. Whether people are more savvy to auto-tuning now than they have been, we're not sure. Every contestant is treated in the same way, if they have a dreadful voice, they still have a dreadful voice."
Fourm member Boysforpele said that the vocal tampering was the "lowest thing the show could have done", claiming that he was "disappointed" and concerned about when else it had it been used in the programme.
"It devalues all talent, deceives the public and the fact they used auto-tune on a few acts only is completely abysmal," they said. "I am now wondering whether they also detune vocals to humiliate. I am so disappointed!"
Kargo agreed, commenting: "It's ludicrous that they are using auto-tune on a music talent search, isn't that just ruining the whole point?"
Soundburst added: "Part of the X Factor auditions' special feel is the performance and (lack of) talent via a raw sound. In the crowd it would have sounded clear and unedited - but if they've stuck a tuning process on vocals since the live recording... then... why? What is its purpose?"
Other forum members said that they did not object to the production process changes, but criticised it for being done so crudely.
"Watching Gamu's performance on YouTube... how the hell was that even broadcast?" asked Performing Monk. "It's about as subtle as a brick through your bay window! They have just slapped auto-tune on without even changing any settings to make it sound good, it's just everything snapped in tune which never sounds natural!
"I don't actually care if they tune the vocals or not. Everything else is fake so why not that? What I think is disastrous is how amateur this has made one of ITV's top shows look. An utter mess. It would have been best just to leave the vocals sounding dodgy than to do this. Idiocy. The production team should be mocked."
The X Factor continues next Saturday at 7.30pm on ITV1.