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), while Super Metroid creates bubbling effects, that have been described as being like "someone having bad indigestion problems". In the original game, this theme can also be heard while fighting Kraid and Ridley, effectively making it a boss theme. The original theme can be heard here: [1], the theme from Super Metroid here: [2] and the theme from Zero Mission here: [3].