 Kong's roar was created by mixing the recorded growls of zoo lions and tigers, subsequently played backwards slowly.Spivak himself provided Kong's "love grunts" by grunting into a megaphone and playing it at a slow speed.For the huge ape's footsteps, Spivak stomped across a gravel-filled box with plungers wrapped in foam attached to his own feet, while the sounds of his chest beats were recorded by Spivak hitting his assistant (who had a microphone held to his back) on the chest with a drumstick.