Luka Sulic, Elton John and Stjepan Hauser

Luka Sulic, Elton John and Stjepan Hauser

Marcus Selhoff/Sony Classical via Bloomberg

From left, Luka Sulic, Elton John and Stjepan Hauser. The rock legend asked the pair to be the opening act of his current world tour after seeing a YouTube.com clip of the cellists playing Michael Jackson's ``Smoth Operator.''