In 1968, Wendy Carlos had a Top 40 hit with a synth-pop instrumental song called "Switched-On Bach" and that success inspired a bunch of other attempts from Moog synthesizer-based bands. But the most of the successful of the bunch was an anonymous band who called themselves Hot Butter.
"Popcorn" was first recorded by Gershon Kingsley in 1969 and he later re-recorded it with his First Moog Quartet in 1971. But the following year, Stan Free (who was a member of the FMQ) recorded it once again with his cover band Hot Butter and that version became a worldwide hit. It hit #1 in places ranging from Australia to the Netherlands and it hit #9 on the U.S. Billboard Top 40 charts. The single sold more than two million copies worldwide and even though Hot Butter only released two albums and a handful of other singles, "Popcorn" is notable for being only of the most insane instrumentals to ever become a hit single.
Even by 1970s standards, "Popcorn" is simplistic and listening to it in 2019, it sounds like something a kid would create randomly pounding synth track buttons on a $5 keyboard. But it was an actual worldwide hit and as you can see in the video below, people really danced to it. Although whomever was the director of this TV segment was likely yelling "quick, another shot of breasts" to the camera crew during the performance.