The famous "Godzilla March" (a rendition of which you hear here) has appeared in various places. Ifukube originally wrote the Godzilla March as part of his beautiful violin concerto (1948). Ifukube started scoring movies in 1947. Because he was often given only 3 days to compose for films, much of his scores (espcially his kaiju eiga soundtracks) were largely comprised of his own classical (concert) works, creating a sort of "Fantasia" experience.