EXCLUSIVE: How Seismic Data and a Dying Piano Gave 'San Andreas' Its Epic Soundtrack

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Raise your hand if you saw San Andreas over the weekend.

Dwayne "The Rock" Johnson's disaster pic opened to a whopping $54.6 million in ticket sales, so we're going to go ahead and guess that most of you have your hands up right about now. (And even if you haven't made it out to the theater yet, this exclusive behind-the-scenes footage is still crazy cool.)

San Andreas composer Andrew Lockington is giving ET a sneak peek at the method behind his madness in a new featurette. In the video above, watch as he destroys a perfectly fine piano with a sledgehammer and wire-cutters to create the pitch-perfect soundtrack for the fall of the Golden Gate Bridge... creepy!

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"We had only planned to record hitting it with the hammers, and those sounds are blended in with the orchestral elements in the film," says Lockington. "After that, I sat down to play this broken instrument that was hanging on by a thread, and I could play notes, but they didn't sound like they were supposed to, and it no longer even sounded like a piano. So suddenly we had this whole new instrument – and some of those sounds figure prominently in certain scenes as well. It's an interesting rhythmic element."

Lockington also reveals that the real-life San Andreas Fault contributed to the sounds of the film.

"We subscribed to the feed from the U.S. Geological Seismic Survey," he explains. "Using data gathered specifically from the San Andreas Fault, we collected that information and converted it into musical soundwaves that are used in the score."

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For his part, Lockington is no stranger to epic soundtracks. His previous credits include Journey to the Center of the Earth, Percy Jackson: Sea of Monsters and even The Rock and director Brad Peyton's 2012 project, Journey 2: The Mysterious Island.

Now, go ahead and watch that sledgehammer show the piano who's boss in the player above. (You know you want to.)