The largest of the bowed instruments, but with the smallest volume, this instrument also plays in the lowest register. The double-bass is twice the size of the cello; although the cello is not a small instrument and is, in its turn, twice the size of the viola.
It is true that the double-bass is a development of the ancient viol; this huge instrument was first used in an orchestra in the 17th century. The double-bass is so big that the player has to either stand or perch on a high chair. There are two kinds of double-bass: the German form has sloping shoulders and other features of the Renaissance viol family and is still used in the symphony orchestra; the Italian form differs in having features of the violin family.
The sloping shoulder allows the player to lean over the instrument to produce higher notes. The modern instrument allows greater virtuosity; it is possible to play very speedy sequences. It is a demanding instrument to play; because of its size the player’s fingers have to stretch over large areas and the bow is quite heavy; these features combine to make playing a complicated process, it is difficult to play with a light touch. It is traditionally played either with a bow or by plucking or by rhythmic “slapping” of the strings.

The double-bass has an important role in music; the bass part provides a foundation for the melody. In the orchestra the main function of the double-bass is as support, but it is also used as a solo and ensemble instrument. It is very popular in the jazz genre, here the strings are usually plucked (pizzicato). The main duty of the double-bass player is to control the main theme by a playing succession of harmonies. In this way the rhythm, and thus the form of the piece, is maintained.