A symphony orchestra is made up of musicians playing string, woodwind, brass and percussion instruments. A typical symphony orchestra has between 70 and 100 members.
An orchestra's string section is comprised of five instruments: first and second violin, viola, cello and bass (also called a "double bass"). Harps are sometimes included as well. The woodwind instruments include piccolo, flutes, oboes, clarinets and bassoons. The brass section can include horns, trumpets, tubas, trombones and saxophones. Percussion sections include tympani, snare and bass drums, cymbals, triangles, Glockenspiels, xylophones and tambourines. Pianos often appear with symphonies, as do harpsichords, though more rarely.
The term "symphony orchestra" often refers to a full orchestra with all, or the majority, of the above-named instruments. Another name for a symphony orchestra is a "philharmonic orchestra." Chamber orchestras are smaller, often made up only about 50 musicians, most of whom play stringed instruments.
Baroque orchestras, the earliest orchestras formed, included only strings, horns and trumpets, tympani, harpsichords, flutes, oboes and bassoons. As music evolved, the classical orchestra emerged, adding clarinets. The early romantic orchestra added piccolos, bass clarinets and contrabassoons, along with tubas and trombones, and all additional percussion instruments. It was the first regularly to include a harp. Late romantic orchestras added pianos and celestas. Modern orchestras feature the above instruments, along with saxophones, French horns and a wider variety of percussion instruments, such as wood blocks.
Other instruments, such as electric or acoustic guitars, electric basses and synthesizers, can be added as called for in individual compositions.