Previous years' X Factor finals have attracted duets from the likes of megastars Beyonce, Rihanna, Kylie Minogue and Michael Buble, while this year it's left to the judges themselves to serenade their acts into the winning spot (we can't help but wonder what Louis would have done if his acts had gone through!).
Putting even more pressure on the judges to help secure the X Factor 2011 winner's title for their acts, this thrilling sing-off will no doubt go down in X Factor history.
Kelly and Amelia Lily will sing River Deep, Mountain High, while Tulisa and Little Mix are to sing a mash-up of If I Ain't Got You and Empire State Of Mind, and the boys - Gary and Marcus will team up to perform More Than A Woman.
With everything left to sing for, this year's competition is the closest yet!