Sound a tune at the same time as covering Split Enz? (7)

I believe the answer is:

whistle

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But I can't explain it at all! Could you help me understand?

(Other definitions for whistle that I've seen before include "Blow through teeth" , "Warning sound" , "Simple fipple flute" , "Hits Lew to make shrill sound" , "For something, ask in vain" .)

I've seen this clue in the Sydney Morning Herald.

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