|This article is written from the Real Life point of view|
Tourian is the theme of the area of the same name in Metroid, Super Metroid and Metroid: Zero Mission. While Metroid and Zero Mission make the theme sound mechanical, as that is the elemental theme Tourian goes by (mechanical), Super Metroid creates bubbling effects since part of the new Tourian takes place in a barren area.
In the original game, this theme can also be heard while fighting Kraid and Ridley, effectively making it a boss theme. A techno, sped-up remix of the theme is heard in Area 8 in Metroid: Samus Returns as Samus is hunting the final few Larva Metroids. It continues to be heard until Samus drops down into the Queen Metroid's chamber.