X-Factor producers vow to broadcast every flat note

The sound filter is often used by record producers to mask bum notes in recording studios, but came under the spotlight when viewers complained about its use on the ITV1 show last weekend.

But the programme's producers have pledged that the technique will not feature in either the audition shows or in the live rounds.

A spokeswoman said: "This week's show is currently still in edit which is normal practice. Therefore this week's show has not had to be re-edited."

Many viewers voiced concerns after watching the performance by teenager Gamu Nhengu when the latest series began on Saturday.

Her version of the Katrina And The Waves hit Walking On Sunshine prompted a flurry of online claims that producers had auto-tuned her voice.

The 18-year-old from Clackmannanshire, Scotland, she was unanimously ushered through to the next round with Simon Cowell telling her she was "really talented".

Earlier this week programme chiefs said sound filters were not used to give a competitive advantage, but remove additional noises.

They said: "We do not use, and never have used, audio technology that would unfairly reflect any singer's original performance on The X Factor.

"In line with standard television practice, sound processing filters are used to remove background noise on our pre-recorded shows."