Some of my orgy history --
60's-70's -- Sexual Freedom league, very organized to start, very wild by the end but very hetero / Sex clubs like Plato's retreat, very hetero, lots of different rooms, all sorts of different activity. Friends parties, a bit more self conscious, since everyone knew one another, but that also could be fun.
80's - 2000's Sex on nude beaches after dark; organized orgies using the web (these often required coming as a couple but not always) -- some were bisexual, some only bi for women, all controlled their access in one way or another by the internet. These were held in a hotel suite or in a loft. They could be gloriously hot. Often they began with some sort of demo that would get everyone in the mood, then the clothes would have to come off. There were also, for a while, lesbian events that began with a real sex show and then turned into orgies. These were both in SF and New York. I got to see a couple by standing in the back, but friends of mine went to them a lot.