Acoustic Tuning Fork

A metal hairpin caught my eye right near the wooden chair leg! It was wedged tight between two floorboard seams. I marched over, wedged the tip of my yellow pen under the curved loop, and levered it up with a firm heave. Clink! The black hairpin popped free and landed with a sharp rattle. I picked it up by the rounded end, braced its two thin prongs against the pen's plastic barrel, and gave one prong a brisk flick with my thumbnail. Twiiiiing! A high, silvery hum buzzed straight through the plastic into my fingers like a miniature tuning fork! An exceptional portable acoustic instrument!