Simplify the following text for a Grade 12 native English-speaking person.
Original: zhongqing gauge ) with a container of ` string gum ' ã ç è ã , ã -- ä é ç ç å 1\/4 ã -- Shangyin Shanghai Conservatorie Quality Qin Strings ( metal-nylon ) , ã -- è ä å ç ç ã -- Huqiu Silk Strings ) ) Until recently , the guqin 's strings were always made of various thicknesses of twisted silk , but since then most players use modern nylon-flatwound steel strings .
Simplified: Until the Cultural Revolution , the guqin 's strings were always made of various thicknesses of twisted silk ã ç ã , but since then most players use modern nylon-flatwound steel strings ã é 1\/4 ç ã .