Steven Spielberg has a habit of building up a lot of suspense to his monsters and creatures before actually showing them.

In "Jaws," the shark doesn't pop his head out of the water until the film's third act. The aliens of "Close Encounters of the Third Kind" don't appear until the film's final moments.

Spielberg used the same trick for the T. rex in "Jurassic Park," to terrifying effect. Before making its first appearance, the giant dinosaur is heard through roars and grunts and, most memorably, a plastic cup of water, which vibrates as the predator stomps along and draws near:

Universal The ingenious shot came to Spielberg while listening to an Earth, Wind, and Fire song with the bass "turned up full volume" in his car. The identity of the song remains unknown.

A behind-the-scenes featurette from Universal, which can be found on the "Jurassic Park" Blu-ray, shows some of the original storyboards for the iconic shot:

The cup of water shakes as T. rex wanders in the distance. Universal

The original storyboards for this memorable scene show the characters before the arrival of the park's most terrifying dinosaur. Universal "I was at work and Steven calls into the office and he goes, 'I'm in the car. Earth, Wind, and Fire is playing, and my mirror is shaking! That's what we need to do!'" Dinosaur effects supervisor Michael Lantieri said in a making-of featurette on the "Jurassic Park" Blu-ray. "He goes, 'We need to shake the mirror, and then I wanna do something with the water.'"

Universal It took a lot of work to make Spielberg's vision come to life.

"The mirror shaking was easy ... put a little vibrating motor in and shook it." Lantieri said. "But the water was another story. It was a very difficult thing to do. You couldn't do it. "

So Lantieri gathered everybody he could find to try to figure out how to make that water shake.

Interestingly enough, it was music that first inspired this shot and music that eventually brought it to life. Lantieri decided to experiment with his guitar.

"I set a glass and started playing notes on a guitar and got to a right frequency ... a right note ... and it did exactly what I wanted it to do." Lantieri said.

To replicate that for the shot, they "fed a guitar string through the car, down to the ground, and then I had a guy lay under the car and pluck the guitar string," Lantieri said in an interview from an early "Jurassic Park" DVD.

Universal "One of the things that Steven is so good at is finding images that represent the story, the emotion, that the audience is supposed to be experiencing," cinematographer Dean Cundey said in the same behind-the-scenes video.

But to find that right image, you might need to hear a good tune first.

Watch the behind-the-scenes clip below via Universal: