Before I tell you how I have been writing new verses to Yiddish songs (and how you can do it too), let me share this catty and amusing passage by Shmuel Leyb Tsitron from his derogatory chapter about Eliakum Tsunzer (Zunser) in his book Literary Generations.
As far as I can tell, Tsitron's main gripe is that Tsunzer got a swelled head from being so lauded and feted as a singer and songwriter while Tsitron and all his earnest cronies were shivering in garrets. Tsitron here reveals that Zunser used (gasp) a hand-made rhyming dictionary, implying that a "real" poet would not stoop so low:
Something happened which left me completely cold to the business of Eliakum's anniversary. One day I went around to his aparment to talk with him about the celebration. I didn't find him at home, and was obliged to wait. One of his little boys, who knew me well, came to me and gave me his hand, holding all the while in his other hand a little handwritten booklet. I took the book and and had a look in it.
I immediately saw its contents: long lists of words which rhyme. Eliakum fell ten times lower in my estimation ten times lower in that very moment. I had always doubted his "art" and thought him no more than a rhyme-maker; but I hadn't known his rhymes were written down and re-used.
Thus I also discovered the secret of his quick verse making, which I mentioned in an earlier chapter. And it was a person like this we'd decided to celebrate as a poet? Wasn't this some sort of desecration of something holy, a profanation against the real true art? That's what I was thinking then.
I told a few of our acquaintances about this and said we should completely give up the idea of the anniversary. They didn't agree and felt this had nothing to do with the anniversary, because in the end one sees what great use he had in bringing our ideas into the world. I had to give in to the majority.
A short time later I had the opportunity to ask Eliakum whether it's true what they say, that there are poets who have prepared written down lists of all kinds of rhymes?
Eliakum answered: "Quite certainly a poet can't get along without such a list."
I didn't want to get into a dispute with him and show him how wrong and full of holes this was. I only asked him: "Can you, by chance/curiosity, at least show me one of our poets who uses such a list?"
"I've shown you already. Take, for instance, the Hebrew Poet Dr. Yitskhok Kaminer. I myself have seen him with a whole notebook written full of Hebrew rhymes."