 The three treble guitar strings are made from sheep or cow intestine, referred to as plain gut, while the three bass strings are made of a silk thread core wound with gut.Since the development of nylon guitar strings by Albert Augustine Ltd. in 1948, the three treble strings are a single nylon filament, while the three bass strings are made of a core of fine nylon threadlike filaments wound with silver-plated bronze or copper wire.Up until the Second World War animal gut and silk were the materials from which guitar strings were manufactured.