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Aural malapropisms
You are quite right to say that Lady Mondegreen has a life of her own. She is a mischievous creature, and her utterings are sometimes a little salacious, as: "Buy, buy me some merkin pie." Don McLean cleaned this one up for his audience of good old whisky drinking chevy drivers.
Mondegreens and malapropisms are not exactly the same. Mondegreens are just mishearings, whereas malapropisms reflect a certain mangling of words and are the fault of the speaker. --Mary Jackson
The phrase "aural malapropism" conveys exactly the same idea and contains the same elements, translated to another sense, of a verbal mistake that only one party, either the utterer or the hearer of what is uttered, makes.
In the case of the malapropism, the mistake is made by the utterer of the words and the audience recognizes it as a mistake as expressing the imperfect understanding of the utterer. In the case of the aural malapropism, the mistake is made by the listener, who "mangles" the words in his understanding of them as he hears or mishears them, because he hasn't grasped the full sense of what the phrase must mean (hence "laid him on the green" becomes "Lady Mondegreen" for the hearer who hasn't paid sufficient attention to the context, thus has not been able to understand words that could, without that attention, lead to homophonic confusion.
I think "aural malapropism" is fine. But then I also ride allegories along the banks of the Nile.
Erratum sheet:
For "ride" read "fill in"
For "allegories" read "the blank"
For "along the banks" read "within the solander"
For "the Nile" read "her smile"