pouët.net

Im fairly certain that it was released before the 20xxsuper series of nvidia gpus. But not by much, loads of eye candy...
I've tried narrowing it down, searching through page after page, looking through groups, and no luck as of yet.

It was likely a 4k-64k (personal bias) but could be a "regular" demo.
*******TLDR
*In the beginning, the camera is flying through a rainbow kaleidoscope chamber.
*Then after that there's a reflective silver saucer (ET) flying over water and mountains,
with flashing lights.
*Before it loops, IIRC, two 2 twisted neon ropes are twisting and lighting up in an atrium
of sorts.

That last part may have been part of another prod..... I am fairly certain it was in this one though. You can have bonus if you know it's from something else, and mention which it is.

Thanks for reading if you made it this far.

this? dunno if thats what you're looking for

you pretty much described every psydemo ever, including mine

Instant Zen or Aeon Flux, maybe?

My first thought was Masagin .

My apologies if I wasn't specific enough and it was more like 'insert generic demo here'.
I may try digging through my mess of a hdd again. Alls good and well.

Let us know if you found it

That was a returning motif in Synesthetics demos.

except it was red and not silver and not a saucer but spaceship shaped, but yes, you are right about it being reflective and able to fly :P