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Seasoned secret-spotter @memory_fallen has uncovered yet another interesting Easter Egg that has apparently gone undetected for decades.
The game in question this time is the Saturn port of the 1996 arcade racer Sega Touring Car Championship, which launched on the console in 1997.
It turns out this conversion has a secret remix of the Sega Rally song Conditioned Reflex, which can only be accessed if you have Sega Rally save data on your system.
While the existence of the song has been known for a while – you can listen to the game's soundtrack by popping the disc into a standard CD player, and it's track 18 – it doesn't seem that anyone has actually found a way to access the song in-game until now.
Directed by Kenji Sasaki and produced by Tetsuya Mizuguchi, the coin-op version of Sega Touring Car Championship ran on the Model 2 board. In addition to being ported to Saturn, it received a Microsoft Windows conversion in 1998.