|This article is written
from the Real Life
point of view
The original Metroid version differed depending on whether the game was the NES or Famicom Disk System version. In the NES version, there is a simple "whoop whoop" sound, while the Famicom version features a screeching siren.
The NES version also features an uplifting part that was removed in later versions, which made it sound closer to the original Japanese theme.
The original theme from the NES version can be heard here: , the Famicom version ripped from the Super Metroid: Sound in Action CD here:  (track contains several sound effects), the Zero Mission theme here:  and the theme from Echoes here: .