The double bass is a musical instrument, the largest and lowest- tuned member of the violin family of string instruments, which includes the violin, viola, and cello. It resembles the other members of the family, but is much larger and has slight differences in shape. Other names for the instrument (especially when used in folk, bluegrass, and jazz music) include string bass, acoustic bass, bass violin, doghouse bass, dog-house, bull fiddle, contrabass, and upright bass.