Dolly Parton wrote and first recorded 'I Will Always Love You' in 1973, but it was Whitney Houston's 1992 cover for The Bodyguard soundtrack that made it immortal, becoming one of the best-selling singles of all time. Houston's a cappella opening and the sustained high note became the definitive vocal performance of the nineties. Online, the climax is a staple of dramatic montages, talent-show auditions and parody edits, where the sheer power of the note sells both genuine emotion and exaggerated comedy.