tuning key

British  

noun

1. a device that may be placed over a wrest pin on a piano, etc, and turned to alter the tension and pitch of a string

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Example Sentences

The screws were rusty and hard to move, and the tuning key was old, and would slip.

From Harper's Young People, June 29, 1880 An Illustrated Weekly by Various

I dare say the tuning key was too old, or perhaps you understand modern pianos better.

From Harper's Young People, June 29, 1880 An Illustrated Weekly by Various