I first found the track from this short 1986 off-air TV recording in Brazil:
Shazam pointed me to this unfortunate hip-hop song from Japan which sampled not a few bars but the ENTIRE song in 2017, which is weird. The original track really seems abandoned to time.
I cleaned it a bit with lala.ai to give a better idea of the track:
So there is. This mysterious song was used 30 year apart in opposite sides of the planet. What is it? Keith Emerson? Rick Wakeman?
You could ask deadbundy if they remember what the sample was.
_alexpine_ on discord. 2018 was HOW many years ago?!?! 2 correct unidentified/lost media solves out of my probably hundreds of bad guesses isn't THAT bad of a track record, right?