Well, there is such a thing as a "poem code". Its not exactly the best method of secure communication, but what do you expect out of people who get their jollies by fucking robots? They're not exactly cryptographic technicians.
Anyway, during the second world war, the SOE and OSS used them in the same manner that numbers stations transmit what seems like nonsense but in a far less secure manner.
At certain times, the BBC or VOA would have their people read a poem or a phrase that I guess you could loosely call a "cyphertext". The people receiving it, usually in German or Japanese occupied territory but sometimes in neutral areas, would have the "key", generally a book or piece of music, and be able to decrypt what the cyphertext meant.
It was fairly expedient, but wasn't exactly what you would consider a secure or all that stable one-way communications method because the enemy usually had the key too, and since the cyphertext was transmitted in the clear their counterintelligence people could figure out what was being said based on it, and sometimes due to variances in editions of books what the agents were receiving made no sense because they were using a different version of the key.
Using One-Time Pads and either morse or cleartext voice reading numbers or letters (like the Russians still do) is a much better method for secure one way communication but you run into the problem of key distribution, which is enough of difficult a problem in peacetime and can be an impossible problem during an occupation or conflict.