Tanaka’s Metroid score is the defining example of his atmosphere-first compositional approach. Rather than filling the NES’s 5 channels with melody, he used sparse drone, pulsing texture, and deliberate silence to convey the alien isolation of Planet Zebes.
The Brinstar theme is the most analysed: Pulse 1 carries the primary melodic line, Pulse 2 supports with harmony, and the Triangle provides an atmospheric bass pedal. The Noise and DMC channels are used minimally - the implied silence is the composition.