The Canadian Tenors are the most experienced singing group available. They have performed for the Queen on television several times, including at the Emmys, the Winter Olympics in Vancouver, and Windsor Castle. In 2010, it would have taken a lot to surprise them, but Oprah managed to do so.
She had heard that all of the band members were huge fans of Celine Dion, even though she had never met any of them. They sung their hit song, Hallelujah, on her show and invited famous Canadian singer Leonard Cohen to come on stage with them.
