Metroid was developed by Nintendo R&D1, Gunpei Yokoi’s team - the same division that produced the Game & Watch series and would later create the Game Boy. The core design team was led by Hiroji Kiyotake on character design and Yoshio Sakamoto as director, working alongside Makoto Kano on game design. The project began in 1985 and reached Famicom Disk System shelves in August 1986.

The creative direction was a deliberate departure from Nintendo’s established output. Where Mario was defined by momentum and reward density, Metroid was built around isolation, exploration, and the sensation of being genuinely alone in a hostile environment. The Alien film series was a clear tonal reference. The planet Zebes was designed as a labyrinth without signposting: no arrows, no tutorial, no map. Players were expected to remember the layout themselves.

Tanaka joined the project after the core design was set. His brief, as reconstructed from retrospective accounts, was to score a world that felt empty - not the joyful emptiness of a landscape, but the frightening emptiness of somewhere you are not supposed to be. He had composed energetic, melody-driven scores for Balloon Fight and Excitebike (both 1984). Metroid required something entirely different.

The FDS hardware gave Tanaka a sixth audio channel - the wavetable synthesiser - unavailable on standard NES cartridges. This channel could produce arbitrary waveforms, giving the FDS version of Brinstar a richer, more textured ambient quality. When the NES cartridge port was produced for North American release in August 1987, Tanaka’s compositions had to be adapted within the five standard NES channels. The core architecture survived intact; the timbre changed perceptibly.

The Famicom Disk System version shipped with no on-screen staff credits - unusual even by 1986 standards. The NES port also omitted credits. Tanaka’s authorship was confirmed only through external sources: later interviews, internal Nintendo records, and retrospective game history coverage. For years, many Western players did not know who had written one of the most influential scores in NES history.

Metroid is an open-world action-platformer built around the acquisition of power-ups that unlock previously inaccessible areas. Samus begins nearly defenceless and expands her capabilities through the Morph Ball, Bomb, various beam weapons, Missiles, and movement enhancements like the High Jump Boots and Screw Attack. The world is a continuous interconnected labyrinth - Zebes has no discrete level breaks, no screens telling the player where to go, and no in-game map.

This design was radical for 1986. The exploration loop - enter unknown territory, find an upgrade, return to areas previously blocked, explore further - created a player experience of genuine discovery and genuine disorientation. Getting lost was not a failure state; it was the game. The structure would be codified as “Metroidvania” decades later, but in 1986 it had no name.

Tanaka’s music is load-bearing architecture in this loop. Each area of Zebes has a distinct theme that communicates not just location but psychological state. Brinstar (the surface) is the most melodically accessible. Kraid’s Lair is heavier and more oppressive. Norfair, the deepest zone, is the most dissonant and abstract. The music tells the player, without text or instruction, that they are descending into somewhere worse.

The NES / Famicom’s audio processor (Ricoh RP2A03 in NTSC; RP2A07 in PAL) provides five audio channels:

1. Pulse 1 - square wave, variable duty cycle
2. Pulse 2 - square wave, variable duty cycle
3. Triangle - triangle wave, fixed amplitude, no volume control
4. Noise - pseudo-random noise (percussion, effects)
5. DMC - Delta Modulation Channel (1-bit PCM samples)

For the Brinstar theme, Tanaka’s channel assignments (as documented in chiptune community analyses) are approximately:

• Pulse 1: primary melodic line
• Pulse 2: supporting harmony or counter-melody
• Triangle: atmospheric bass pedal tone
• Noise: minimal - percussion used extremely sparingly
• DMC: unused or near-silent in most of the score

The absence of full noise percussion - standard in NES game music - and the near-absence of the DMC channel creates the distinctive empty quality that made Metroid’s caves feel genuinely vast. When the noise channel does appear, it functions as textural accent rather than rhythmic backbone. This is what separates Tanaka’s Metroid approach from every other NES score of the era: the used channels are not the point. The near-unused channels are.

Koji Kondo - composing for Mario and Zelda simultaneously - filled his channel budgets with melody, countermelody, and rhythmic drive. Both approaches are masterworks. They are simply doing opposite things. Where Kondo’s music energises, Tanaka’s isolates.

Metroid sold moderately in Japan on FDS launch - strong enough to justify the North American cartridge port, but not the runaway success of Mario or Zelda. The game’s difficulty and lack of hand-holding divided contemporary opinion: some players found the non-linear structure liberating; others found it impenetrable.

In North America, the NES release in August 1987 found a more receptive audience. Computer Entertainer - one of the period’s leading NES review publications - praised the game’s atmosphere and scope, noting that it achieved something few NES titles had managed: a sense of genuine scale and isolation. The music was consistently cited in reviews as central to this effect, though reviewers lacked the technical vocabulary to describe precisely what Tanaka had done with the hardware.

Nintendo Power’s coverage in its early issues established Metroid as one of the must-own NES library titles - a position it held throughout the late 1980s. British publications including Computer and Video Games gave the NES version high marks, again foregrounding the atmospheric qualities of both the visual and audio design. Famitsu’s retrospective coverage gave the original 30 out of 40, noting the game’s lasting influence on action-adventure design.

Contemporary players noted the music as something distinct from the rest of the NES library without always articulating why. The retrospective critical consensus, formed across the following two decades, is that Tanaka’s score represented a compositional approach that had no real precedent on the platform - and would not be fully understood until later writers and musicians could describe atmospheric game audio as a deliberate design category.

Tanaka’s Metroid score did more than accompany a game - it created a character. Before the visual design of Samus was understood by most Western players (the reveal of her gender at game’s end was one of gaming’s first major plot twists), it was the music that defined who she was: alone, capable, moving through a world that did not acknowledge her existence.

The score’s treatment of silence as a compositional element - the implied emptiness of near-unused channels - perfectly matched the visual emptiness of Zebes’s corridors. Music and environment reinforced each other in a way that few NES games achieved, and that became a template for atmospheric game design that persists to the present.

Super Metroid (1994) on SNES expanded the blueprint with a richer audio palette and a fully orchestrated approach. The Metroid Prime trilogy (2002-2007) placed the franchise into first-person perspective and built its audio around Kenji Yamamoto’s compositions - which are in direct dialogue with Tanaka’s Brinstar and Norfair themes. Metroid: Other M (2010) revisited the atmospheric approach. Metroid Dread (2021) cited the original NES score as a tonal touchstone.

The concept of “atmospheric” game audio - music designed to create a sense of place and psychological state rather than to entertain in isolation - has antecedents elsewhere, but Metroid 1986 is the most widely cited early example on mass-market home console hardware. Its influence is visible in the survival horror genre (Resident Evil, Silent Hill), the Souls series, and any game that uses sparse audio to build dread.

Tanaka himself moved on from composing after EarthBound (1994), eventually becoming president of Creatures Inc. The hirokazu-tanaka.fan-site explores his full career on the people page and across the music collection.