Area4 5 Basic is heard in the entrance of Area 2, where Samus Aran collects the Lightning Armor Aeion Ability Artifact, and the second half of Area 4, where Samus is chased by the Diggernaut and battles the first Zeta Metroid. It consists largely of an echoing melody played on a glockenspiel or some similar instrument, a harmony performed with bass instruments, and various ambient sounds. The theme resembles Sector 5 (ARC) Low-Temperature Zone Area from Metroid Fusion. It can be heard here: 
Area4 5 Basic may be based upon the ambient track originally played in Phase 3 in Metroid II: Return of Samus. This theme, originally composed by Ryoji Yoshitomi, has some similar note patterns to Area4 5 Basic; the most obvious similarity is the last four notes, which are identical in both songs. Since Phase 3 corresponds directly to Area 2, this may have been a deliberate reference by Daisuke Matsuoka, although this is not confirmed. This ambient theme can be heard here: 
- Despite its internal file name, Area4 5 Basic is not played at all in Area 5.