The term Orchestra comes from the ancient Greeks, who called orkestai to the choir, which accompanied by zithers and aulos (instrumentalists), danced in front of the altar consecrated to the God Dyonisios. In the 17th century the Italians created the Opera in the manner of the ancient Greek tragedies and adopted the name of Orchestra to designate to the group of instrumentalists who accompanied the singers. In a modern theater, the part of the auditorium reserved for the musicians, located between the stage and the public, is called orchestra pit or orchestra. Currently the term Orchestra is used to designate a group of instrumentalists and more or less numerous instruments, which perform a musical work, with the instructions of a director; among which the Symphony Orchestra is the most important.

The modern Symphony Orchestra is made up of a number of performers that varies between 60, 100 or more musicians, who play a variety of instruments which represent the last evolutionary stage of the multiple experiences that have been carried out in the previous four centuries.

The instruments of the Orchestra are divided into four sections, more properly called Families. These families respond to a group based on the way of producing the sound.

There is the family of strings, which is the most important and numerous in the orchestra (60% of the instruments), made up of the violin, the viola, the cello, the double bass, the harp, the guitar and the piano. The Woodwind family made up of the flute, the piccolo, the oboe, the English horn, the bassoon, the contrabassoon, the clarinet, and the bass clarinet.

They are followed by the Brass family made up of the horn, the trumpet, the trombone and the tuba. And lastly, there is the Percussion family, which is comprised of defined tone instruments such as the timpani, the xylophone, the celesta, the carillon and the tubular bells; and those with an indefinable tone such as the bass drum, the cymbals, the castanets, the triangle, among others.

There are also other types of orchestra, such as the chamber orchestra, where the number of instruments needed is smaller, and is usually made up of 25-30 people; until the 18th century this was the most common modality. Another type are the orchestras formed only by a family of instruments; for example, a string orchestrain which only violins, violas, cellos and double basses take part.