There was a lot of Vincent Price back then. It may have been
House on Haunted Hill. I'm not sure, but one of his films was hyped on the theater marquee as "Filmed with Emergo!" Sounds exciting right? Is it like 3D or Cinerama? Well no, it was a silliest gimmick ever from Hollywood.
There was a scene in the movie where the people in the house were being threatened by a skeleton, but it turns out that Vincent Price was scaring them with a skeleton puppet, which he operated with a huge crank in another room, but before you realized Price was manipulating the skeleton, there was a loud "thrash" at the back of the theater, which caused the viewers in the theater to turn around and be surprised by a life sized skeleton that had been concealed behind a curtain "emerge" above everyone's heads and come jiggling along a cable to the front of the theater.
I think the original "thrash" as the curtain sprung opened may have been a surprise, but nowhere near a jump scare, and the skeleton was some plastic blow up thing with a skeleton painted on it. Rather than scare anyone, people were jumping up trying to grab at it and throwing popcorn boxes at it, some still half full.
And that was Emergo, the latest Hollywood special effect, but as far as I know never used again. Must have been a mess to clean up for the theater owner. God, it was dumb.