Vs. Reo

"Vs. Reo" is an unnamed theme from Metroid: Other M. It was composed by Kuniaki Haishima and orchestrated by Sachiko Miyano.

Description
This theme is first played when Samus Aran is ambushed by Reos in the Main Sector, serving as the first battle theme heard aboard the BOTTLE SHIP. It is heard again shortly afterward when Samus is clearing out the Reo-infested Fly Pods in the System Management room. Additionally, this theme is used in the second battle against Nightmare in its room in Sector 2 / Cryosphere, replacing a different theme used in the first battle; however, it does not seem to take any inspiration from Nightmare's original battle theme in Metroid Fusion.

Like many other battle themes in Other M, this theme is evocative of James Horner's score for Aliens. It consists primarily of shrieking high-pitched strings and aggressive metallic percussion (the latter sometimes playing a "heartbeat" rhythm), intended to create a terrifying and adrenaline-rushing mood. These sections are broken up by tense, shrill ambience that crescendos into the next section.

This theme can be heard here: