According to one source, a number of the Korean musicians prefer horsehair bows to the sticks. And I believe the silk-stringed instruments were derived from horsehair. It's difficult to think the Chinese inherited the er-hu WITH silk strings already on it. There is simply no way nomads had any methods of producing silk on their own. I doubt the Arabs did either. Silk production is a Chinese art and other peoples traded for it and some may have possibly learned the art from the Chinese. Why the Chinese replaced horsehair with silk is anyone's guess--maybe they thought horsehair strings too barbaric and that silk showed a distinctly Chinese sensibility or maybe the silk sounded better or maybe silk was simply more plentiful or maybe it was all these--who knows.

Silk is actually very strong and probably stronger than horsehair. I have heard that spider silk is stronger than steel of the same gauge and stronger than silkworm silk but far harder to collect. An outfit made of spider silk would be too expensive for most people to afford. I'd like to see a bow made from spider silk.

I should also mention that all those instruments that used silk strings generally use metal strings today. I was referring to how they were originally strung. But it also shows how materials change over time and that it's usually related to what's easier to produce. Today, steel strings are easier to make than silk ones. I don't know which sounds better.