That era's aesthetic can be strange and surreal at times, almost psychedelic.
So maybe the musician on the comic panel is feeling uncomfortable with playing this kind of gig due to the strange atmosphere, even though as any working class professional musician should say, any paying gig is good.
As knowing random facts is second nature to us trivia fans, it's easy to forget that the average person probably only knows a couple pop cultural references from the 30's.
For me, I have to believe this kind of thing is common knowledge for my generation, which is Gen X, which is what makes this joke from 1981 possible.
I'm old enough that I watched a lot of Looney Tunes and some Fleischer cartoon shorts on broadcast TV when I was a kid, and Gary Larson is almost 20 years older than me, and may have watched them in theaters or on TV.
Today, kids are watching a diverse array of media on the internet, and for those classic cartoon shorts are probably something that they might never come across if they're not actively looking for it, much less any facts about them, and therefore are truly obscure trivia.
That's the impression that I got from comments prior to mine.
I believe it's referring to a barn dance They were popular at the time of the strip, except in this case, the band booked a barn dance with actual barn animals. I think the drawing style looks different because this is an early one, 1981.
The top half is drawn completely different (looking like a classic far side) than the lower shaded half (looking more like an old cartoon). I'm sure the difference in drawing style has something to do with the joke, but I'm not sure how.
In the drawing, I don't think that's how Larson usually depicts cows and other animals, so I'm guessing there's some media reference or context here that we don't recognise or know.