the story behind this song is amazing . Bing was dying and he knew it so he wanted to pass the torch. So David Bowie was asked to sing with Bing. The banter was unscripted. And the duet came about because bowie hated little drummer boy. so a song was written just for him to sing with Bing the result was magic. Note how gaunt Bing looks. one month after this he would be dead.