In the late '80s and '90s, when an adult (parent, uncle, teacher, priest) wanted to embarrass a teenager, all he had to do was to deliver a social commentary or advice by trying to rap. That's exactly how "Promiscuous" feels -- out of place. This song is actually a set of lyrics rapped over sequenced drums, sound effects, and a bit of bass playing from Scott Thunes. The subject: an appearance on television by U.S. Surgeon General Doctor Koop, who under Ronald Reagan's presidency explained to the nation that AIDS was passed on to humans from one green monkey who's blood came in contact with one human. Frank Zappa saw in Koop's theory and general demeanor yet another moral exaggeration by right-wing Republicans -- an excuse to preach against sexual activities: "He says it is not good for us/We just can't be promiscuous/He's a doctor -- he should know/It's the work of the Devil, so/Girls, don't blow!"
"Promiscuous" was performed only once, early in the 1988 tour (on February 26 to be precise). It is this performance that ended up on the album Broadway the Hard Way. Why only once? Someone (maybe a teenager) must have asked Zappa never to do it again, please?