

It's no accident that people get the willies every time the Joker appears on screen in *The Dark Knight. *

"I wanted to write something people would truly hate," says composer Hans Zimmer, describing the unsettling theme music that plays each time actor Heath Ledger's in the house. Zimmer offers the back story on *The Dark Knight * DVD, which drops Tuesday.

As revealed in the two-disc package, Zimmer (Pirates of the Caribbean, The Da Vinci Code) compiled 90,000 bars of experimental music. He used some pretty bizarre methods, including striking razor blades against piano strings.

*Dark Knight *director Chris Nolan, who listened to the entire thing during a flight to Hong Kong to scout locations for the film, says exploring the score "was a pretty unpleasant experience, frankly."

In the end, Zimmer brought in a cellist to perform the Joker's minimalist theme by sawing away at a slowly stretched single note.

The *Dark Knight *score, divvied up between Zimmer and James Newton Howard, is reportedly back in contention for an Oscar after being disqualified for having too many composers on the official cue sheet.

Offered in three sizes ($29 single disc, $35 two-disc special edition and $36 Blu-ray disc), the Dark Knight package also sheds light on the Bat-Pod development process. Described at one point as "anti-aircraft on wheels," Nolan prototyped the contraption in his Los Angeles garage.

*Photo courtesy Warner Bros. *

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