What is this close-up picture? (WotsThat: piano string winding)

Question

What object is shown in this zoomed-in close-up photo?

Accepted Answer

piano string winding. Piano strings aren't actually solid all the way through—the thicker bass strings are copper wire wound tightly around a steel core, kind of like a tiny electrical cable, which lets piano makers create deep, resonant tones without needing strings as thick as your pinky finger. This winding technique was a major innovation because it allowed pianos to get much louder and richer-sounding without becoming impossibly heavy or taking up more space.

Answer: piano string winding

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