I hope it's not true as I like this show and it would make it a farce.
Obviously the vocals are pre-recorded, but I take it on faith that the celebrity is in the costume at all times.
But some 'insider' has alleged that :
The celebrity is not even in the costume at any time other than the unveiling. At other times it is a double or dancer.
Be rest assured the celebrities are indeed underneath the masks at every performance.
While I have my own doubts they're the ones in costume during filming for the
clue packages (separate conversation), all celebrities are 100% present on set and sing live for the actual episodes. There is obviously an element of recorded vocals and autotune involved, but this is all done in post-production. It has been well documented that all celebrities are required to be on set for many hours both before and during shooting, and there's even photos of the audio recorder/microphone set-up that's in-built behind all the masks (with the celebrity inside) if you really want to look into this more.
The comments made by celebrities also prove this - you can tell they're not making up their experiences about rehearsing and performing for the judges. Gretel Killeen in particular has made some extraordinary comments about what the whole thing was like. All versions worldwide also have extreme security measures and non-disclosure agreements, unlike any other ordinary reality show.
The US version takes it one step further, with huge rules and restrictions surrounding the movement of each celebrity while they're on set in order for their identities never to be revealed. This includes putting masks on their family and friends, who attend in the audience to support them.
It has never been, and never will be, a double or dancer underneath the mask. It's part of the contract of the franchise.
