People who write music often use the viola for harmony notes. It is one of the main instruments in a string quartet, along with two violins and a cello. The viola is found in chamber ensembles of string instruments only, and also in full symphony orchestras where strings, woodwinds, brass, and percussion instruments play together. The viola can also be a solo instrument, but is mostly used in an orchestra. The viola comes in many sizes. The sizes are measured in inches, such as a 14-inch viola. The size of the viola is measured from the bottom to the neck of it (its body's length).