Hans Zimmer has created Oscar-winning compositions for numerous films, including The Lion King and Gladiator, but found one of his greatest challenges in finding music to represent Heath Ledger's Joker in The Dark Knight. Speaking to Australia's The West newspaper, Zimmer expressed the challenge of demonstrating the Joker's penchant for anarchy.

"I've been sitting here all night trying to find out what else to do with those two notes," Zimmer said.

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Zimmer also said that he had no intention of allowing Ledger's untimely death affect his approach to the Joker's theme music. "The worst thing I can do is stray from that course and not be rigorous about his performance," Zimmer said.

In addition to work on The Dark Knight, Zimmer is having a busy year, having worked on the scores for Ron Howard's Frost/Nixon, about former President Richard Nixon, as well as the animated Kung Fu Panda and Madagascar: Escape 2 Africa. As if that wasn't enough, Zimmer is also preparing a worldwide concert tour, his first full-length performances in eight years.

The Dark Knight opens on July 18, 2008, and stars Christian Bale, Heath Ledger, Morgan Freeman, Gary Oldman, Aaron Eckhart and Maggie Gylenhall.