This comes from a recent episode of the British version of The Voice. The judges are will.i.am, Jennifer Hudson, Tom Jones (sorry, Sir Tom Jones) and Olly Murs.
I don't know if this is just totally ad-libbed or actually planned. My instinct is usually to default to "actually planned." But the thing is that it doesn't really matter because ultimately what results is just...too good. And I'm not a great fan of any of the participants (though to be clear I like them fine), but this just hits all the right notes. Literally. And in the end, much as my default guess on such things is "actually planned," there are some things here that make me not willing to swear that in a court of law.