弦用啥做的？

https://www.thestrad.com/accessories/stringtelligence-by-thomastik-infeld-what-are-violin-viola-cello-and-bass-strings-made-out-of/9608.article?fbclid=IwAR09ueH6EtILCufL10QIP6yPmT0obbDpQunkrW1SO3joVJJ6NzMrbPa-gB4#.XcTRO_TF5kg.facebook