There is no singing ensemble with more experience than the Canadian Tenors. They have made multiple television appearances, including at the Emmys, the Vancouver Winter Olympics, and Windsor Castle, where they played for the Queen. It would have taken a lot to shock them in 2010, but Oprah pulled it off.
Although she had never met any of the band members, she had heard that they were all avid Celine Dion fans. They invited the renowned Canadian vocalist Leonard Cohen to join them on stage while they sang their biggest song, Hallelujah, on her show.