An orchestra is a large instrumental ensemble that utilizes various types of musical instruments and is used mostly to perform classical music, including symphonies, concertos and tone poems as well as the accompaniment for operas and ballets.
Orchestras vary greatly in size and can range anywhere from a few dozen players to frequently about a hundred, and sometimes as many as 120. The smaller ones are called chamber orchestras and the larger are often referred to as symphony orchestras, concert orchestras and philharmonic orchestras.
The instruments used by orchestras can be broadly classified into woodwinds, brass, percussion and strings. Although the instruments are fairly standardized, there are differences in the numbers of each instrument type according to orchestra size and according to what is being played, and occasionally seldom-used instrument types are required. Fundamental to every large orchestra is the strings section, which usually has the largest number of players, the majority of whom are violin players.