Violin
The violin is the soprano voice of the string family, meaning it plays higher pitches than the rest. It also often plays the melody.
Viola
The viola is the alto voice of the string family and therefore plays the melody and rich harmonies. It is slightly larger than the violin.
Cello
The cello is the tenor voice of the string family and plays beautiful harmonies. It has a deep sound.
String Bass/Double Bass
The string bass is the largest of the string family. It plays very low pitches. It has a rich, chocolaty sound.