stupid question

Gut strings are made of... gut.
Sheep guts (intestines) in fact.
Check this site for info on gut string-making:

http://www.daniellarson.com/article.htm

Hope this helps.

 

The environmentally aware may regard it as recycling a dead sheep.

 

Ahh, there's nothing like the sound of a ribbon of Mongolian horse hair bound to a stick carved from rare Brazilian rain forest wood drawn over dried sheep intestines!