Doublebass. - The doublebass plays a whole octave lower than the cello. It has four strings like the other members of the violin family; on the bass, they are tuned in fourths. The doublebass is not only the deepest voice of the string section, but it often provides the rhythmic foundation of the orchestra.
Doublebasses vary a lot in size and look. In the 1800s, some builders enjoyed experimenting with super-sized doublebasses. These were really hard to play because of their size. Some were so tall that they require two people to play them; one to do the fingering and another to hold the bow! A few of these huge instruments survive - in museums.
Bass players may choose between two kinds of bows. The German bow has a convex curve, somewhat like the old-style bow-and-arrow bows. The French bow is held differently and has a concave line, like a cello bow.
The doublebass began to be standard in orchestras sometime during the 18th century. Modern orchestras usually have at least eight doublebasses. There is also a surprising amount of solo repertoire for the doublebass. A lot of it requires scordatura tuning, which is a special way of tuning to increase the instrument's range, or to make some positions easier to reach.
Doublebasses in some form began appearing in the early 1500s, like the rest of the string family. Their design continued to change a lot for the next three or four centuries. For a while in the 18th century, three strings were normal, and then five.
The doublebass began to become really popular in Haydn's and Mozart's time. This was partly because virtuoso bass players from Italy were touring the continent. One of the best, Domenico Dragonetti, settled in England and made the bass a popular instrument there. He was friends with Haydn, Beethoven, Liszt, Rossini, and many other composers.
Another Italian bassist, Giovanni Bottesini, was also a composer. He studied composition with Verdi and, in addition to operas, wrote some concertos for two doublebasses!