The violin has three instruments that look like it, but just in different sizes. First, the violin, is the smallest of four and makes a higher pitched sounds than the others. Next is the viola: the viola is slightly bigger than the violin but it makes a lower sound. Then comes the cello, which was used in the 1970 pop/disco music. Finally comes the bass, the biggest of the three others. It is usually played when propped up against you and the ground, and makes the deepest and lowest sounds of the other three. All of these are in the string instrument category, and there are many other stringed instruments that would be in this category but these are the most commonly used.