The elements of the story - Grandpa's Beat-up Banjo are altered because the author paints a character who seems frail and whose equipment seemed damaged to put a twist to the unexpected outcome of the story.
This is a story that modifies the David and Goliath story into a version where the expected becomes unexpected.
Rather than a physical fight and a giant vs a little lad, there is the Musical competition and a Grandpa with his very old musical instrument.
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https://brainly.com/question/5660357