Vs. Charge Beam Beast

"Vs. Charge Beam Beast", identified as 04 in the Sound Test, is a theme from Metroid: Zero Mission.

Description
This theme is first heard in Brinstar when Samus Aran encounters the Charge Beam Beast. If she fails to kill it during this first encounter, the theme will play again during subsequent battles until she succeeds in killing it. This theme is heard again in Kraid's Lair, where Samus battles the Acid Worm.

This fast-paced battle theme is relentlessly frantic and chaotic, intended to get the player's heart racing during the boss fights. The unusual rhythms serve to further make the player feel uneasy. It constantly fluctuates in pitch, with the overall direction rising to higher pitches, building up tension before climaxing with high-pitched syncopated staccato notes.

The theme can be heard here: