Large group of musicians playing together on different instruments. In Western music, an orchestra is usually based on the bowed, stringed instruments of the violin family, to which is usually added the woodwind, brass, and percussion sections. The number of players per section and the instruments used may vary according to the needs of the composer.
History The term was originally used in Greek theatre for the semicircular space in front of the stage, and was adopted in 17th-century Italy to refer first to the space in front of the stage where musicians sat, and later to the musicians themselves.
Western instruments In the 17th century, the orchestra was a chance combination of whatever instruments might be available. For a while, viols and violins were played alongside each other but gradually the viols were dropped in preference to the superior projection quality and versatility of the violin, violas, and cellos.
By the beginning of the 18th century, the string section had developed into a self-contained unit usually divided into two groups of violins (first and second), violas, cellos, and double basses. Other instruments were also added when needed, singly or in pairs, mostly flutes, oboes, bassoons, and horns. A continuo keyboard player was also a part of the orchestra, building up the chords from a bass-line to fill out the harmonies. The woodwind section became standardized by the end of the 18th century. It now contained pairs of flutes, oboes, clarinets, and bassoons, to which were later added piccolo, cor anglais, bass clarinet, and double bassoon. At that time, two timpani and two horns were also standard, and two trumpets were occasionally added.
During the 19th century, the brass section was gradually expanded to include four horns, three trumpets, three trombones, and tuba. To the percussion section a third timpano was added, and from Turkey came the bass drum, side drum, cymbals, and triangle. One or more harps became common and, to maintain balance, the number of string instruments to each part was increased. Other instruments used in the orchestra include xylophone, celesta, glockenspiel, piano (which replaced the harpsichord in the late 18th century), and organ.
In the 20th century, composers often preferred smaller groupings of instruments, sometimes in unconventional combinations. The orchestra used to be conducted by means of a violin bow, but by Felix Mendelssohn's time the baton took over.
Non-Western ensembles The term may also be applied to non-Western ensembles such as the Indonesian gamelan orchestra, founded on families of percussion instruments, mainly tuned gongs and bells.
Role of a conductor
BBC Symphony Orchestra
Royal Philharmonic Orchestra
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