double bass, bowed stringed musical instrument, the contrabass of the modern orchestral string section. It originated as a double-bass viol, an instrument described as early as 1566. A true double-bass violin appeared during the 18th cent. but was rejected as unwieldy and of poor tonal quality. The present double bass is tuned in fourths and usually has a flat back and sloping shoulders but has never attained a definitive form. The bow, the last to give up its convex shape, was long held palm upward like the viol bow, but the violin style is now customary. Indispensable in the orchestra, it also has a place in the dance band and jazz.

Lowest-pitched of the modern stringed instruments. It varies in size, up to 80 inches (200 cm) tall. Its shape also varies; its shoulders usually slope more than those of the violin, reflecting its status as a hybrid of the viol and violin families (the name comes from the double-bass viol). It emerged from these families in the late Renaissance, and it has always been less standardized in form than its cousins in the violin family. It normally has four strings; the orchestral instrument often has a lower fifth string (more often, an extension is added to the fourth string), and the jazz instrument has a higher fifth string. Its range is an octave below that of the cello. It is normally bowed in orchestral music and plucked in jazz. In rock bands and some jazz bands, the electric bass is used instead.

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