References to early uses of “soapless radio” can be found in the 2012 psychological journal “Social Psychology: Revisiting the Classic Studies” written by Joanne R. Smith and S. Alexander Haslam. Why did it appear in a psychological magazine? It seems the authors found the “soapless radio” gag a perfect way to document societal pressures and group mentality. You see, the joke was passed off as an obscure reference to, as is often the case, nothing at all.
The way the phrase was used went like this: An actor or performer, long established in his company, would welcome a new insider into his social circle. While conversing, the established artist chatted with a colleague within earshot of the new initiate, intentionally blurting out “No soap! Radio!”, a deliberately nonsensical phrase, like the punchline of a joke. The entire room was trained to burst out laughing at the “reference.” Then everyone would turn to the new initiate to see if they “got” the fake joke. If the initiate laughed, the room knew they had been tricked into pretending the sentence had meaning. If they didn’t, sometimes the established artist would force the issue, i.e. “Don’t you get it? No soap opera! Radio!” Sometimes the initiate would be hounded into admitting that he understood, even though he didn’t/couldn’t. The pressure felt by the “brand” was an ideal way to study physiological pressure to conform.
It is unknown why the phrase “soapless radio” was selected, although some scholars have traced the origin of “soapless” as a silly joke dating back to the 1770s.