弦樂三重奏 樂譜
A string trio is a group of three string instruments, or any musical piece written for such a group. The first known string trios were written for two violins and a violoncello, though the format changed around the second half of the 18th century, replacing one of the violins with a viola. This formation of violin, viola, and cello survives to this day as the standard definition for 'string trio'. The string trio never enjoyed the popularity of the string quartet, probably because of its limitations in terms of voicing and harmony.