The phrase
"blue polka" typically refers to a type of music or dance. "Blue" refers to the musical genre or style, often associated with blues music, which has a soulful and melancholic sound. "Polka" refers to a lively and upbeat dance style originating from Central Europe. So,
"blue polka" suggests a combination of these two contrasting styles, representing a lively dance with a touch of sadness or nostalgia in the music.
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