KALAMAZOO -- When Janice Newton, 67, of Kalamazoo, watches musicians on TV or attends a concert, she often wonders about their guitar strings. Just possibly, she had a hand in making those strings.

I saw a video last year on YouTube where a Russian maker built a rather elaborate rig to turn PET plastic bottles into a flat, very narrow noodle-like “string” that proved to be surprisingly strong.

In a 240,000-square-foot factory an hour east of New York City, several hundred workers buzz from shift to shift making strings for guitars, violins, Greek bouzoukis and Turkish ouds, some 700,000 per ...