We were watching an "Instructional Video" on swinging when we saw
something that made our minds really churn... a "Key Party".

For those of you who don't know, its either set up in an extremely
large home or a rented floor at a motel, etc... The male places his
key in the basket and picks up another key from the basket. Whatever
room ID or number that key has is who he plays with that night. The
wife usually stays in her own room.

My questions are these: Have you ever attended one of these parties?
How many people were there? Am I explaining it right, or are there
other variations? If you haven't attended a party like this, would
you? Why or why not?

That is one variation.

Another is that all parties gather and men's keys are tossed into a central container. Women draw keys and are partnered for the evening. Since most women recognize the keys of their SO, they'll avoid those.

I've also heard of the same sort of thing with playing cards. The women draw a card, memorize it, and place it in a hat, for example. Men draw the cards and pair up.

The random nature is a rush. The hitch is that everybody's got to be willing to connect according to the draw, even if it turns out to be the "troll" of the party or the SO!