One single track from a Game Boy Color tie-in to the Muteki-Oh Tri-Zenon mecha anime. This 2001 premium disc came bundled with the handheld game, and the whole thing is just one recording on a tiny 8cm CD. Probably a chiptune rendition of the show's theme or a short medley pulled from the GBC cartridge.
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The kind of thing that existed purely as a bonus item in the box, the real collectible being the disc itself rather than what was on it. Tri-Zenon was a mecha show that aired in 2000 and got the usual multimedia push with games and merchandise.
Hardware limitations meant whatever's on here is running through that classic Game Boy Color sound chip, all square waves and noise channels. If you collect obscure mecha game ephemera from the early 2000s, this is the kind of single-track curiosity that ends up being the rarest thing on your shelf.