At the Eurovision Song Contest, performers get three minutes to make a big impression. Grabbing viewers’ attention as one of 25 acts competing in quick succession in Saturday’s grand final in Vienna means pulling out all the stops, both musically and visually. In the case of this year’s favorites to win, the Finnish duo of pop singer Pete Parkkonen and classical violinist Linda Lampenius, that involves jets of flame, a valuable 18th-century violin and a team of “ninjas” working to avert disaster. The pair’s song “Liekinheitin,” or “Flamethrower,” is a favorite with both fans and betting markets with its melding of pop and classical influences — and its spectacular staging. Here’s what it takes to create the eye-catching performance. Permission to play Parkkonen and Lampenius dub their sound “new pop with a classical touch." Their song of burning love is an explosion of energy in which Parkkonen’s passionate vocals act as counterpoint to Lampenius’ frenetic fiddling.…