Hideo Kojima decided to have Harry Gregson-Williams compose most of the game's soundtrack after Kojima and sound director Kazuki Muraoka watched "The Replacement Killers" in a cinema, and enjoyed the music that Williams composed for the film. They had planned to watch "Saving Private Ryan", but the line for the movie was very long.

Gregson-Williams was given limited descriptions of the music he had to compose, such as "heroic" or "stealthy" as Kojima wanted the music to be pure Gregson-Williams. Gregson-Williams was told that the limited instructions he got was due to language barriers.