An orchestra (ˈɔːrkɪstrə; ) is a large instrumental ensemble typical of classical music, which combines instruments from different families. There are typically four main sections of instruments:
bowed string instruments, such as the violin, viola, cello, and double bass
woodwinds, such as the flute, oboe, clarinet, and bassoon
brass instruments, such as the horn, trumpet, trombone, cornet, and tuba
percussion instruments, such as the timpani, snare drum, bass drum, cymbals, triangle, tambourine, and mallet percussion instruments
Other instruments such as the piano, harpsichord, and celesta may sometimes appear in a fifth keyboard section or may stand alone as soloist instruments, as may the concert harp and, for performances of some modern compositions, electronic instruments, and guitars.
A full-size Western orchestra may sometimes be called a or philharmonic orchestra (from Greek phil-, "loving", and "harmony"). The number of musicians employed in a given performance may vary from seventy to over one hundred, depending on the work being played and the venue size. A (sometimes a concert orchestra) is a smaller ensemble of not more than about fifty musicians. Orchestras that specialize in the Baroque music of, for example, Johann Sebastian Bach and George Frideric Handel, or Classical repertoire, such as that of Haydn and Mozart, tend to be smaller than orchestras performing a Romantic music repertoire such as the symphonies of Ludwig van Beethoven and Johannes Brahms. The typical orchestra grew in size throughout the 18th and 19th centuries, reaching a peak with the large orchestras (of as many as 120 players) called for in the works of Richard Wagner, and later, Gustav Mahler.
Orchestras are usually led by a conductor who directs the performance with movements of the hands and arms, often made easier for the musicians to see by using a short wooden rod known as a conductor's baton. The conductor unifies the orchestra, sets the tempo, and shapes the sound of the ensemble.