As someone in the culture 20-30 years ago, it was always something that was underground... not promoted in a traditional sense, and hosted in unpermitted spaces. Usually you wouldn't know until the day of the event where the location actually was.
Much of the time it would be in industrial areas that were pretty deserted and dark at night, far away from any life that would complain about the noise that would go on until at lease sunrise. If outdoors it might be out in the woods, on the edge of an Indian reservation, in the desert, etc. Often there was a gritty sense of danger and some really odd characters you would meet, certainly not helped by the substances they might be on.
What you linked is what I'd call outdoor parties/festivals. Maybe folks today call them raves, but these things existed back then and we certainly didn't.
~15 years ago I remember a friend convincing me to drive a bunch of us to a rave that involved meeting a guy in grocery store parking lot between certain hours and writing down the instructions he gave us. We then drove an hour on the freeway, got off and spent 30 minutes on a series of forest service roads to get to a 2(3?) stage rave in a clearing in the woods. It went at least until sunrise, we left as the sun came up.
I went to them 25 years ago as well. I get the same thing from the organized promoted ones as I got from the old ones. I didn't need it to be "underground". I just needed the people, the music, the vibe.
The main difference for me was the social aspects and tapestry of characters you'd meet. Not only were they much longer (if you're a night person), they tended to be significantly less crowded for the space they were in. There were time and space advantages for that aspect to blossom.
There were events where I met so many people that it had a snowball effect. In addition to anyone there I already knew, I'd be building/merging new friend groups on the fly and sometimes hours would go by before I'd see any of the people I came with.
Conversely, at sanctioned events I'd stick tight with my friends pretty much all night... sure you'd meet other people, but not nearly to the same level. Generally dance more and socialize less.
The events you’re talking about still exist to a T. If anything, there’s too much interest in them, and now they’re hiding not just from cops but from “tourists”. Think finance bros who just want the exclusivity and a chance to bother women
Much of the time it would be in industrial areas that were pretty deserted and dark at night, far away from any life that would complain about the noise that would go on until at lease sunrise. If outdoors it might be out in the woods, on the edge of an Indian reservation, in the desert, etc. Often there was a gritty sense of danger and some really odd characters you would meet, certainly not helped by the substances they might be on.
What you linked is what I'd call outdoor parties/festivals. Maybe folks today call them raves, but these things existed back then and we certainly didn't.