Wow, I never really dwelled on the foot fall sound too much but I think you are spot on. It's really almost a part of the musical score. I think I can recall Guy Tucker at a G Fest explaining how the foot falls were devised by Ifukube himself.

I also seem to have a vaugh recollection reading some where that because of technological limitations, GOJIRA's music and special sound effects were more or less recorded live and together like an old radio show. The music and sound effects seem to compliment each other in a way modern film makers could learn from!
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