Met2 Caverns4

Caverns 3 is an ambient theme from Metroid II: Return of Samus and its remake Metroid: Samus Returns. It was originally composed by Ryoji Yoshitomi and later remixed by Daisuke Matsuoka.

Description
In Return of Samus, Caverns 3 is heard in Phase 4, where it plays in the tunnels and caves surrounding the Chozo ruins; it also plays throughout Phase 6. This atmospheric theme consists of a low throbbing drone, high-pitched clicking, and a frantic melody, all working together to create an uneasy and unsettling auditory experience. Unlike other ambient tracks in the game, such as Caverns 2, there is very little silence. It can be heard here:

In Samus Returns, Caverns 3 received a full remix that plays in the middle section of Area 3, inside the Chozo robotics factory; unlike the original game, it does not play at all in Area 4. It is very faithful to the original track, with the throbbing drone interpreted as a distorted low choir. It can be heard here:

Trivia

 * Ironically, despite both Caverns 3 and SR388 Underground receiving remixes in Area 3, their respective locations have switched. In Return of Samus, Caverns 3 plays in the low catacombs, and SR388 Underground plays inside the Chozo ruins. In Samus Returns, SR388 Underground plays in the low catacombs, and Caverns 3 plays in the interior of the second Chozo building.