A nice read and good history lesson!
Making its debut in 1954, Godzilla roars its way into cinematic history, with some Hollywood historians saying that his scream tops King Kong's in terms of iconic-ness. When first molding the beast’s shriek, audio engineers tried the standard splicing of various animal noises, but the sound proved too "earthly" for a creature from the radioactive abyss. Needing a roar that truly signifies his god-like stature, filmmakers went outside the Foley realm and invited composer Akira Ifukube, who was also composing the film's soundtrack, to have a go at the task. Ifukube instinctually looked toward musical instruments and realized that friction would be the key to making the perfect unsettling disonance required. So he coated a leather glove in tar resin and rubbed it along the string of a double bass. Somewhat similar to nails-on-a-blackboard, but lower-pitched, the screech was so obscure that it made perfect for the prehistoric monster, Godzilla. What’s interesting to note is that each iteration of Godzilla afterwards has it’s own unique sound process for achieving the legendary roar.