An orchestra is an ensemble of musicians who play musical compositions that are designed to be performed by a large group of instruments. In order to be considered an orchestra, the ensemble must have several sections, including string instruments, woodwinds, and brass instruments, with most also having a percussion section. It is led by a conductor in performance and can perform a wide variety of musical pieces at all sorts of events.
The word is derived from the Greek word for the area of the stage where the chorus sang and danced during performances in Ancient Greece. In staged performances with an orchestra, the musicians are classically positioned in a pit in the front of the stage, which closely mirrors the design used in Greece. While performing on its own for a concert, the musicians are often positioned on a stage so that people can see them.
If an orchestra has fewer than 50 players, it is known as a chamber orchestra. Chamber orchestras can vary widely in size, and they may have more than 50 players on staff, allowing for substitutions as needed while providing a pool of specialized talent. A harpist, for example, may be necessary in some pieces but not in others. These groups tend to perform smaller, more intimate pieces. The music can get quite complex, especially when it calls for a large complement of players.
Orchestras with 100 or more members are known as “full” orchestras, and they are sometimes referred to as symphony or philharmonic orchestras. There is no difference between those two terms, and in fact some cities have one of each, with people using the terms to differentiate between two different groups of performers. Ballets, operas, and other performances that include music are often performed with a chamber orchestra, rather than a full one, depending on the composition being performed.
The huge ensemble of instruments in a full orchestra can allow the musicians to perform very large and very complex pieces. Various sections can harmonize with each other in a variety of ways, and the group may be supplemented with a chorus for works that include vocal elements. Some of the greatest works of classical music were composed for full orchestras, and seeing them in person can be a very illuminating experience, as watching the musicians can provide interesting clues into the ways that the different sections work with each other.