Nope, that's not it. In fact, I don't think I've heard those versions before on the ST!
I'm really banging my head against a wall here trying to "see" the demo it might have been in.
All I'm seeing is a full screen demo with either a full screen scroller (ULM-like) or a big sprite (like the screen in The European Demos with the big Wizball sprite).
I've had a look through my demo collection, but there have been demos I had at one point in time but didn't keep. It could have been on them
It's not from a demo by ULM as Gunstick doesn't recognise it and he did all the sampling for ULM. Although it would be nice to know where he got all those samples for the main menu in darkside!
Anyway, it's a sample of the intro to the song probably not even lasting 5 seconds before looping. Have a listen to the actual song and see if it rings any bells.
Thanks for the input.